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  • Oracle Support Master Note for Troubleshooting Advanced Queuing and Oracle Streams Propagation Issues (Doc ID 233099.1)

    - by faye.todd(at)oracle.com
    Master Note for Troubleshooting Advanced Queuing and Oracle Streams Propagation Issues (Doc ID 233099.1) Copyright (c) 2010, Oracle Corporation. All Rights Reserved. In this Document  Purpose  Last Review Date  Instructions for the Reader  Troubleshooting Details     1. Scope and Application      2. Definitions and Classifications     3. How to Use This Guide     4. Basic AQ Propagation Troubleshooting     5. Additional Troubleshooting Steps for AQ Propagation of User-Enqueued and Dequeued Messages     6. Additional Troubleshooting Steps for Propagation in an Oracle Streams Environment     7. Performance Issues  References Applies to: Oracle Server - Enterprise Edition - Version: 8.1.7.0 to 11.2.0.2 - Release: 8.1.7 to 11.2Information in this document applies to any platform. Purpose This document presents a step-by-step methodology for troubleshooting and resolving problems with Advanced Queuing Propagation in both Streams and basic Advanced Queuing environments. It also serves as a master reference for other more specific notes on Oracle Streams Propagation and Advanced Queuing Propagation issues. Last Review Date December 20, 2010 Instructions for the Reader A Troubleshooting Guide is provided to assist in debugging a specific issue. When possible, diagnostic tools are included in the document to assist in troubleshooting. Troubleshooting Details 1. Scope and Application This note is intended for Database Administrators of Oracle databases where issues are being encountered with propagating messages between advanced queues, whether the queues are used for user-created messaging systems or for Oracle Streams. It contains troubleshooting steps and links to notes for further problem resolution.It can also be used a template to document a problem when it is necessary to engage Oracle Support Services. Knowing what is NOT happening can frequently speed up the resolution process by focusing solely on the pertinent problem area. This guide is divided into five parts: Section 2: Definitions and Classifications (discusses the different types and features of propagations possible - helpful for understanding the rest of the guide) Section 3: How to Use this Guide (to be used as a start part for determining the scope of the problem and what sections to consult) Section 4. Basic AQ propagation troubleshooting (applies to both AQ propagation of user enqueued and dequeued messages as well as Oracle Streams propagations) Section 5. Additional troubleshooting steps for AQ propagation of user enqueued and dequeued messages Section 6. Additional troubleshooting steps for Oracle Streams propagation Section 7. Performance issues 2. Definitions and Classifications Given the potential scope of issues that can be encountered with AQ propagation, the first recommended step is to do some basic diagnosis to determine the type of problem that is being encountered. 2.1. What Type of Propagation is Being Used? 2.1.1. Buffered Messaging For an advanced queue, messages can be maintained on disk (persistent messaging) or in memory (buffered messaging). To determine if a queue is buffered or not, reference the GV_$BUFFERED_QUEUES view. If the queue does not appear in this view, it is persistent. 2.1.2. Propagation mode - queue-to-dblink vs queue-to-queue As of 10.2, an AQ propagation can also be defined as queue-to-dblink, or queue-to-queue: queue-to-dblink: The propagation delivers messages or events from the source queue to all subscribing queues at the destination database identified by the dblink. A single propagation schedule is used to propagate messages to all subscribing queues. Hence any changes made to this schedule will affect message delivery to all the subscribing queues. This mode does not support multiple propagations from the same source queue to the same target database. queue-to-queue: Added in 10.2, this propagation mode delivers messages or events from the source queue to a specific destination queue identified on the database link. This allows the user to have fine-grained control on the propagation schedule for message delivery. This new propagation mode also supports transparent failover when propagating to a destination Oracle RAC system. With queue-to-queue propagation, you are no longer required to re-point a database link if the owner instance of the queue fails on Oracle RAC. This mode supports multiple propagations to the same target database if the target queues are different. The default is queue-to-dblink. To verify if queue-to-queue propagation is being used, in non-Streams environments query DBA_QUEUE_SCHEDULES.DESTINATION - if a remote queue is listed along with the remote database link, then queue-to-queue propagation is being used. For Streams environments, the DBA_PROPAGATION.QUEUE_TO_QUEUE column can be checked.See the following note for a method to switch between the two modes:Document 827473.1 How to alter propagation from queue-to-queue to queue-to-dblink 2.1.3. Combined Capture and Apply (CCA) for Streams In 11g Oracle Streams environments, an optimization called Combined Capture and Apply (CCA) is implemented by default when possible. Although a propagation is configured in this case, Streams does not use it; instead it passes information directly from capture to an apply receiver. To see if CCA is in use: COLUMN CAPTURE_NAME HEADING 'Capture Name' FORMAT A30COLUMN OPTIMIZATION HEADING 'CCA Mode?' FORMAT A10SELECT CAPTURE_NAME, DECODE(OPTIMIZATION,0, 'No','Yes') OPTIMIZATIONFROM V$STREAMS_CAPTURE; Also, see the following note:Document 463820.1 Streams Combined Capture and Apply in 11g 2.2. Queue Table Compatibility There are three types of queue table compatibility. In more recent databases, queue tables may be present in all three modes of compatibility: 8.0 - earliest version, deprecated in 10.2 onwards 8.1 - support added for RAC, asynchronous notification, secure queues, queue level access control, rule-based subscribers, separate storage of history information 10.0 - if the database is in 10.1-compatible mode, then the default value for queue table compatibility is 10.0 2.3. Single vs Multiple Consumer Queue Tables If more than one recipient can dequeue a message from a queue, then its queue table is multiple consumer. You can propagate messages from a multiple-consumer queue to a single-consumer queue. Propagation from a single-consumer queue to a multiple-consumer queue is not possible. 3. How to Use This Guide 3.1. Are Messages Being Propagated at All, or is the Propagation Just Slow? Run the following query on the source database for the propagation (assuming that it is running): select TOTAL_NUMBER from DBA_QUEUE_SCHEDULES where QNAME='<source_queue_name>'; If TOTAL_NUMBER is increasing, then propagation is most likely functioning, although it may be slow. For performance issues, see Section 7. 3.2. Propagation Between Persistent User-Created Queues See Sections 4 and 5 (and optionally Section 6 if performance is an issue). 3.3. Propagation Between Buffered User-Created Queues See Sections 4, 5, and 6 (and optionally Section 7 if performance is an issue). 3.4. Propagation between Oracle Streams Queues (without Combined Capture and Apply (CCA) Optimization) See Sections 4 and 6 (and optionally Section 7 if performance is an issue). 3.5. Propagation between Oracle Streams Queues (with Combined Capture and Apply (CCA) Optimization) Although an AQ propagation is not used directly in this case, some characteristics of the message transfer are inferred from the propagation parameters used. Some parts of Sections 4 and 6 still apply. 3.6. Messaging Gateway Propagations This note does not apply to Messaging Gateway propagations. 4. Basic AQ Propagation Troubleshooting 4.1. Double-check Your Code Make sure that you are consistent in your usage of the database link(s) names, queue names, etc. It may be useful to plot a diagram of which queues are connected via which database links to make sure that the logical structure is correct. 4.2. Verify that Job Queue Processes are Running 4.2.1. Versions 10.2 and Lower - DBA_JOBS Package For versions 10.2 and lower, a scheduled propagation is managed by DBMS_JOB package. The propagation is performed by job queue process background processes. Therefore we need to verify that there are sufficient processes available for the propagation process. We should have at least 4 job queue processes running and preferably more depending on the number of other jobs running in the database. It should be noted that for AQ specific work, AQ will only ever use half of the job queue processes available.An issue caused by an inadequate job queue processes parameter setting is described in the following note:Document 298015.1 Kwqjswproc:Excep After Loop: Assigning To Self 4.2.1.1. Job Queue Processes in Initalization Parameter File The parameter JOB_QUEUE_PROCESSES in the init.ora/spfile should be > 0. The value can be changed dynamically via connect / as sysdbaalter system set JOB_QUEUE_PROCESSES=10; 4.2.1.2. Job Queue Processes in Memory The following command will show how many job queue processes are currentlyin use by this instance (this may be different than what is in the init.ora/spfile): connect / as sysdbashow parameter job; 4.2.1.3. OS PIDs Corresponding to Job Queue Processes Identify the operating system process ids (spids) of job queue processes involved in propagation via select p.SPID, p.PROGRAM from V$PROCESS p, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j where s.SID=jr.SID and s.PADDR=p.ADDR and jr.JOB=j.JOBand j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%'; and these SPIDs can be used to check at the operating system level that they exist.In 8i a job queue process will have a name similar to: ora_snp1_<instance_name>.In 9i onwards you will see a coordinator process: ora_cjq0_ and multiple slave processes: ora_jnnn_<instance_name>, where nnn is an integer between 1 and 999. 4.2.2. Version 11.1 and Above - Oracle Scheduler In version 11.1 and above, Oracle Scheduler is used to perform AQ and Streams propagations. Oracle Scheduler automatically tunes the number of slave processes for these jobs based on the load on the computer system, and the JOB_QUEUE_PROCESSES initialization parameter is only used to specify the maximum number of slave processes. Therefore, the JOB_QUEUE_PROCESSES initialization parameter does not need to be set (it defaults to a very high number), unless you want to limit the number of slaves that can be created. If JOB_QUEUE_PROCESSES = 0, no propagation jobs will run.See the following note for a discussion of Oracle Streams 11g and Oracle Scheduler:Document 1083608.1 11g Streams and Oracle Scheduler 4.2.2.1. Job Queue Processes in Initalization Parameter File The parameter JOB_QUEUE_PROCESSES in the init.ora/spfile should be > 0, and preferably be left at its default value. The value can be changed dynamically via connect / as sysdbaalter system set JOB_QUEUE_PROCESSES=10; To set the JOB_QUEUE_PROCESSES parameter to its default value, run: connect / as sysdbaalter system reset JOB_QUEUE_PROCESSES; and then bounce the instance. 4.2.2.2. Job Queue Processes in Memory The following command will show how many job queue processes are currently in use by this instance (this may be different than what is in the init.ora/spfile): connect / as sysdbashow parameter job; 4.2.2.3. OS PIDs Corresponding to Job Queue Processes Identify the operating system process ids (SPIDs) of job queue processes involved in propagation via col PROGRAM for a30select p.SPID, p.PROGRAM, j.JOB_namefrom v$PROCESS p, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j where s.SID=jr.SESSION_ID and s.PADDR=p.ADDRand jr.JOB_name=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%'; and these SPIDs can be used to check at the operating system level that they exist.You will see a coordinator process: ora_cjq0_ and multiple slave processes: ora_jnnn_<instance_name>, where nnn is an integer between 1 and 999. 4.3. Check the Alert Log and Any Associated Trace Files The first place to check for propagation failures is the alert logs at all sites (local and if relevant all remote sites). When a job queue process attempts to execute a schedule and fails it will always write an error stack to the alert log. This error stack will also be written in a job queue process trace file, which will be written to the BACKGROUND_DUMP_DEST location for 10.2 and below, and in the DIAGNOSTIC_DEST location for 11g. The fact that errors are written to the alert log demonstrates that the schedule is executing. This means that the problem could be with the set up of the schedule. In this example the ORA-02068 demonstrates that the failure was at the remote site. Further investigation revealed that the remote database was not open, hence the ORA-03114 error. Starting the database resolved the problem. Thu Feb 14 10:40:05 2002 Propagation Schedule for (AQADM.MULTIPLEQ, SHANE816.WORLD) encountered following error:ORA-04052: error occurred when looking up Remote object [email protected]: error occurred at recursive SQL level 4ORA-02068: following severe error from SHANE816ORA-03114: not connected to ORACLEORA-06512: at "SYS.DBMS_AQADM_SYS", line 4770ORA-06512: at "SYS.DBMS_AQADM", line 548ORA-06512: at line 1 Other potential errors that may be written to the alert log can be found in the following notes:Document 827184.1 AQ Propagation with CLOB data types Fails with ORA-22990 (11.1)Document 846297.1 AQ Propagation Fails : ORA-00600[kope2upic2954] or Ora-00600[Kghsstream_copyn] (10.2, 11.1)Document 731292.1 ORA-25215 Reported on Local Propagation When Using Transformation with ANYDATA queue tables (10.2, 11.1, 11.2)Document 365093.1 ORA-07445 [kwqppay2aqe()+7360] Reported on Propagation of a Transformed Message (10.1, 10.2)Document 219416.1 Advanced Queuing Propagation Fails with ORA-22922 (9.0)Document 1203544.1 AQ Propagation Aborted with ORA-600 [ociksin: invalid status] on SYS.DBMS_AQADM_SYS.AQ$_PROPAGATION_PROCEDURE After Upgrade (11.1, 11.2)Document 1087324.1 ORA-01405 ORA-01422 reported by Advanced Queuing Propagation schedules after RAC reconfiguration (10.2)Document 1079577.1 Advanced Queuing Propagation Fails With "ORA-22370 incorrect usage of method" (9.2, 10.2, 11.1, 11.2)Document 332792.1 ORA-04061 error relating to SYS.DBMS_PRVTAQIP reported when setting up Statspack (8.1, 9.0, 9.2, 10.1)Document 353325.1 ORA-24056: Internal inconsistency for QUEUE <queue_name> and destination <dblink> (8.1, 9.0, 9.2, 10.1, 10.2, 11.1, 11.2)Document 787367.1 ORA-22275 reported on Propagating Messages with LOB component when propagating between 10.1 and 10.2 (10.1, 10.2)Document 566622.1 ORA-22275 when propagating >4K AQ$_JMS_TEXT_MESSAGEs from 9.2.0.8 to 10.2.0.1 (9.2, 10.1)Document 731539.1 ORA-29268: HTTP client error 401 Unauthorized Error when the AQ Servlet attempts to Propagate a message via HTTP (9.0, 9.2, 10.1, 10.2, 11.1)Document 253131.1 Concurrent Writes May Corrupt LOB Segment When Using Auto Segment Space Management (ORA-1555) (9.2)Document 118884.1 How to unschedule a propagation schedule stuck in pending stateDocument 222992.1 DBMS_AQADM.DISABLE_PROPAGATION_SCHEDULE Returns ORA-24082Document 282987.1 Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueDocument 1204080.1 AQ Propagation Failing With ORA-25329 After Upgraded From 8i or 9i to 10g or 11g.Document 1233675.1 AQ Propagation stops after upgrade to 11.2.0.1 ORA-30757 4.3.1. Errors Related to Incorrect Network Configuration The most common propagation errors result from an incorrect network configuration. The list below contains common errors caused by tnsnames.ora file or database links being configured incorrectly: - ORA-12154: TNS:could not resolve service name- ORA-12505: TNS:listener does not currently know of SID given in connect descriptor- ORA-12514: TNS:listener could not resolve SERVICE_NAME - ORA-12541: TNS-12541 TNS:no listener 4.4. Check the Database Links Exist and are Functioning Correctly For schedules to remote databases confirm the database link exists via. SQL> col DBLINK for a45SQL> select QNAME, NVL(REGEXP_SUBSTR(DESTINATION, '[^@]+', 1, 2), DESTINATION) dblink2 from DBA_QUEUE_SCHEDULES3 where MESSAGE_DELIVERY_MODE = 'PERSISTENT';QNAME DBLINK------------------------------ ---------------------------------------------MY_QUEUE ORCL102B.WORLD Connect as the owner of the link and select across it to verify it works and connects to the database we expect. i.e. select * from ALL_QUEUES@ ORCL102B.WORLD; You need to ensure that the userid that scheduled the propagation (using DBMS_AQADM.SCHEDULE_PROPAGATION or DBMS_PROPAGATION_ADM.CREATE_PROPAGATION if using Streams) has access to the database link for the destination. 4.5. Has Propagation Been Correctly Scheduled? Check that the propagation schedule has been created and that a job queue process has been assigned. Look for the entry in DBA_QUEUE_SCHEDULES and SYS.AQ$_SCHEDULES for your schedule. For 10g and below, check that it has a JOBNO entry in SYS.AQ$_SCHEDULES, and that there is an entry in DBA_JOBS with that JOBNO. For 11g and above, check that the schedule has a JOB_NAME entry in SYS.AQ$_SCHEDULES, and that there is an entry in DBA_SCHEDULER_JOBS with that JOB_NAME. Check the destination is as intended and spelled correctly. SQL> select SCHEMA, QNAME, DESTINATION, SCHEDULE_DISABLED, PROCESS_NAME from DBA_QUEUE_SCHEDULES;SCHEMA QNAME DESTINATION S PROCESS------- ---------- ------------------ - -----------AQADM MULTIPLEQ AQ$_LOCAL N J000 AQ$_LOCAL in the destination column shows that the queue to which we are propagating to is in the same database as the source queue. If the propagation was to a remote (different) database, a database link will be in the DESTINATION column. The entry in the SCHEDULE_DISABLED column, N, means that the schedule is NOT disabled. If Y (yes) appears in this column, propagation is disabled and the schedule will not be executed. If not using Oracle Streams, propagation should resume once you have enabled the schedule by invoking DBMS_AQADM.ENABLE_PROPAGATION_SCHEDULE (for 10.2 Oracle Streams and above, the DBMS_PROPAGATION_ADM.START_PROPAGATION procedure should be used). The PROCESS_NAME is the name of the job queue process currently allocated to execute the schedule. This process is allocated dynamically at execution time. If the PROCESS_NAME column is null (empty) the schedule is not currently executing. You may need to execute this statement a number of times to verify if a process is being allocated. If a process is at some time allocated to the schedule, it is attempting to execute. SQL> select SCHEMA, QNAME, LAST_RUN_DATE, NEXT_RUN_DATE from DBA_QUEUE_SCHEDULES;SCHEMA QNAME LAST_RUN_DATE NEXT_RUN_DATE------ ----- ----------------------- ----------------------- AQADM MULTIPLEQ 13-FEB-2002 13:18:57 13-FEB-2002 13:20:30 In 11g, these dates are expressed in TIMESTAMP WITH TIME ZONE datatypes. If the NEXT_RUN_DATE and NEXT_RUN_TIME columns are null when this statement is executed, the scheduled propagation is currently in progress. If they never change it would suggest that the schedule itself is never executing. If the next scheduled execution is too far away, change the NEXT_TIME parameter of the schedule so that schedules are executed more frequently (assuming that the window is not set to be infinite). Parameters of a schedule can be changed using the DBMS_AQADM.ALTER_PROPAGATION_SCHEDULE call. In 10g and below, scheduling propagation posts a job in the DBA_JOBS view. The columns are more or less the same as DBA_QUEUE_SCHEDULES so you just need to recognize the job and verify that it exists. SQL> select JOB, WHAT from DBA_JOBS where WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%';JOB WHAT---- ----------------- 720 next_date := sys.dbms_aqadm.aq$_propaq(job); For 11g, scheduling propagation posts a job in DBA_SCHEDULER_JOBS instead: SQL> select JOB_NAME from DBA_SCHEDULER_JOBS where JOB_NAME like 'AQ_JOB$_%';JOB_NAME------------------------------AQ_JOB$_41 If no job exists, check DBA_QUEUE_SCHEDULES to make sure that the schedule has not been disabled. For 10g and below, the job number is dynamic for AQ propagation schedules. The procedure that is executed to expedite a propagation schedule runs, removes itself from DBA_JOBS, and then reposts a new job for the next scheduled propagation. The job number should therefore always increment unless the schedule has been set up to run indefinitely. 4.6. Is the Schedule Executing but Failing to Complete? Run the following query: SQL> select FAILURES, LAST_ERROR_MSG from DBA_QUEUE_SCHEDULES;FAILURES LAST_ERROR_MSG------------ -----------------------1 ORA-25207: enqueue failed, queue AQADM.INQ is disabled from enqueueingORA-02063: preceding line from SHANE816 The failures column shows how many times we have attempted to execute the schedule and failed. Oracle will attempt to execute the schedule 16 times after which it will be removed from the DBA_JOBS or DBA_SCHEDULER_JOBS view and the schedule will become disabled. The column DBA_QUEUE_SCHEDULES.SCHEDULE_DISABLED will show 'Y'. For 11g and above, the DBA_SCHEDULER_JOBS.STATE column will show 'BROKEN' for the job corresponding to DBA_QUEUE_SCHEDULES.JOB_NAME. Prior to 10g the back off algorithm for failures was exponential, whereas from 10g onwards it is linear. The propagation will become disabled on the 17th attempt. Only the last execution failure will be reflected in the LAST_ERROR_MSG column. That is, if the schedule fails 5 times for 5 different reasons, only the last set of errors will be recorded in DBA_QUEUE_SCHEDULES. Any errors need to be resolved to allow propagation to continue. If propagation has also become disabled due to 17 failures, first resolve the reason for the error and then re-enable the schedule using the DBMS_AQADM.ENABLE_PROPAGATION_SCHEDULE procedure, or DBMS_PROPAGATION_ADM.START_PROPAGATION if using 10.2 or above Oracle Streams. As soon as the schedule executes successfully the error message entries will be deleted. Oracle does not keep a history of past failures. However, when using Oracle Streams, the errors will be retained in the DBA_PROPAGATION view even after the schedule resumes successfully. See the following note for instructions on how to clear out the errors from the DBA_PROPAGATION view:Document 808136.1 How to clear the old errors from DBA_PROPAGATION view?If a schedule is active and no errors are being reported then the source queue may not have any messages to be propagated. 4.7. Do the Propagation Notification Queue Table and Queue Exist? Check to see that the propagation notification queue table and queue exist and are enabled for enqueue and dequeue. Propagation makes use of the propagation notification queue for handling propagation run-time events, and the messages in this queue are stored in a SYS-owned queue table. This queue should never be stopped or dropped and the corresponding queue table never be dropped. 10g and belowThe propagation notification queue table is of the format SYS.AQ$_PROP_TABLE_n, where 'n' is the RAC instance number, i.e. '1' for a non-RAC environment. This queue and queue table are created implicitly when propagation is first scheduled. If propagation has been scheduled and these objects do not exist, try unscheduling and rescheduling propagation. If they still do not exist contact Oracle Support. SQL> select QUEUE_TABLE from DBA_QUEUE_TABLES2 where QUEUE_TABLE like '%PROP_TABLE%' and OWNER = 'SYS';QUEUE_TABLE------------------------------AQ$_PROP_TABLE_1SQL> select NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED2 from DBA_QUEUES where owner='SYS'3 and QUEUE_TABLE like '%PROP_TABLE%';NAME ENQUEUE DEQUEUE------------------------------ ------- -------AQ$_PROP_NOTIFY_1 YES YESAQ$_AQ$_PROP_TABLE_1_E NO NO If the AQ$_PROP_NOTIFY_1 queue is not enabled for enqueue or dequeue, it should be so enabled using DBMS_AQADM.START_QUEUE. However, the exception queue AQ$_AQ$_PROP_TABLE_1_E should not be enabled for enqueue or dequeue.11g and aboveThe propagation notification queue table is of the format SYS.AQ_PROP_TABLE, and is created when the database is created. If they do not exist, contact Oracle Support. SQL> select QUEUE_TABLE from DBA_QUEUE_TABLES2 where QUEUE_TABLE like '%PROP_TABLE%' and OWNER = 'SYS';QUEUE_TABLE------------------------------AQ_PROP_TABLESQL> select NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED2 from DBA_QUEUES where owner='SYS'3 and QUEUE_TABLE like '%PROP_TABLE%';NAME ENQUEUE DEQUEUE------------------------------ ------- -------AQ_PROP_NOTIFY YES YESAQ$_AQ_PROP_TABLE_E NO NO If the AQ_PROP_NOTIFY queue is not enabled for enqueue or dequeue, it should be so enabled using DBMS_AQADM.START_QUEUE. However, the exception queue AQ$_AQ$_PROP_TABLE_E should not be enabled for enqueue or dequeue. 4.8. Does the Remote Queue Exist and is it Enabled for Enqueueing? Check that the remote queue the propagation is transferring messages to exists and is enabled for enqueue: SQL> select DESTINATION from USER_QUEUE_SCHEDULES where QNAME = 'OUTQ';DESTINATION-----------------------------------------------------------------------------"AQADM"."INQ"@M2V102.ESSQL> select OWNER, NAME, ENQUEUE_ENABLED, DEQUEUE_ENABLED from [email protected];OWNER NAME ENQUEUE DEQUEUE-------- ------ ----------- -----------AQADM INQ YES YES 4.9. Do the Target and Source Database Charactersets Differ? If a message fails to propagate, check the database charactersets of the source and target databases. Investigate whether the same message can propagate between the databases with the same characterset or it is only a particular combination of charactersets which causes a problem. 4.10. Check the Queue Table Type Agreement Propagation is not possible between queue tables which have types that differ in some respect. One way to determine if this is the case is to run the DBMS_AQADM.VERIFY_QUEUE_TYPES procedure for the two queues that the propagation operates on. If the types do not agree, DBMS_AQADM.VERIFY_QUEUE_TYPES will return '0'.For AQ propagation between databases which have different NLS_LENGTH_SEMANTICS settings, propagation will not work, unless the queues are Oracle Streams ANYDATA queues.See the following notes for issues caused by lack of type agreement:Document 1079577.1 Advanced Queuing Propagation Fails With "ORA-22370: incorrect usage of method"Document 282987.1 Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueDocument 353754.1 Streams Messaging Propagation Fails between Single and Multi-byte Charactersets when using Chararacter Length Semantics in the ADT 4.11. Enable Propagation Tracing 4.11.1. System Level This is set it in the init.ora/spfile as follows: event="24040 trace name context forever, level 10" and restart the instanceThis event cannot be set dynamically with an alter system command until version 10.2: SQL> alter system set events '24040 trace name context forever, level 10'; To unset the event: SQL> alter system set events '24040 trace name context off'; Debugging information will be logged to job queue trace file(s) (jnnn) as propagation takes place. You can check the trace file for errors, and for statements indicating that messages have been sent. For the most part the trace information is understandable. This trace should also be uploaded to Oracle Support if a service request is created. 4.11.2. Attaching to a Specific Process We can also attach to an existing job queue processes that is running a propagation schedule and trace it individually using the oradebug utility, as follows:10.2 and below connect / as sysdbaselect p.SPID, p.PROGRAM from v$PROCESS p, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j where s.SID=jr.SID and s.PADDR=p.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%';-- For the process id (SPID) attach to it via oradebug and generate the following traceoradebug setospid <SPID>oradebug unlimitoradebug Event 10046 trace name context forever, level 12oradebug Event 24040 trace name context forever, level 10-- Trace the process for 5 minutesoradebug Event 10046 trace name context offoradebug Event 24040 trace name context off-- The following command returns the pathname/filename to the file being written tooradebug tracefile_name 11g connect / as sysdbacol PROGRAM for a30select p.SPID, p.PROGRAM, j.JOB_NAMEfrom v$PROCESS p, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j where s.SID=jr.SESSION_ID and s.PADDR=p.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%';-- For the process id (SPID) attach to it via oradebug and generate the following traceoradebug setospid <SPID>oradebug unlimitoradebug Event 10046 trace name context forever, level 12oradebug Event 24040 trace name context forever, level 10-- Trace the process for 5 minutesoradebug Event 10046 trace name context offoradebug Event 24040 trace name context off-- The following command returns the pathname/filename to the file being written tooradebug tracefile_name 4.11.3. Further Tracing The previous tracing steps only trace the job queue process executing the propagation on the source. At times it is useful to trace the propagation receiver process (the session which is enqueueing the messages into the target queue) on the target database which is associated with the job queue process on the source database.These following queries provide ways of identifying the processes involved in propagation so that you can attach to them via oradebug to generate trace information.In order to identify the propagation receiver process you need to execute the query as a user with privileges to access the v$ views in both the local and remote databases so the database link must connect as a user with those privileges in the remote database. The <DBLINK> in the queries should be replaced by the appropriate database link.The queries have two forms due to the differences between operating systems. The value returned by 'Rem Process' is the operating system identifier of the propagation receiver on the remote database. Once identified, this process can be attached to and traced on the remote database using the commands given in Section 4.11.2.10.2 and below - Windows select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from v$PROCESS pl, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SID and s.PADDR=pl.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%' and pl.SPID=substr(sr.PROCESS, instr(sr.PROCESS,':')+1); 10.2 and below - Unix select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_JOBS_RUNNING jr, V$SESSION s, DBA_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SID and s.PADDR=pl.ADDR and jr.JOB=j.JOB and j.WHAT like '%sys.dbms_aqadm.aq$_propaq(job)%' and pl.SPID=sr.PROCESS; 11g - Windows select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SESSION_ID and s.PADDR=pl.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%%' and pl.SPID=substr(sr.PROCESS, instr(sr.PROCESS,':')+1); 11g - Unix select pl.SPID "JobQ Process", pl.PROGRAM, sr.PROCESS "Rem Process" from V$PROCESS pl, DBA_SCHEDULER_RUNNING_JOBS jr, V$SESSION s, DBA_SCHEDULER_JOBS j, V$SESSION@<DBLINK> sr where s.SID=jr.SESSION_ID and s.PADDR=pl.ADDR and jr.JOB_NAME=j.JOB_NAME and j.JOB_NAME like '%AQ_JOB$_%%' and pl.SPID=sr.PROCESS;   5. Additional Troubleshooting Steps for AQ Propagation of User-Enqueued and Dequeued Messages 5.1. Check the Privileges of All Users Involved Ensure that the owner of the database link has the necessary privileges on the aq packages. SQL> select TABLE_NAME, PRIVILEGE from USER_TAB_PRIVS;TABLE_NAME PRIVILEGE------------------------------ ----------------------------------------DBMS_LOCK EXECUTEDBMS_AQ EXECUTEDBMS_AQADM EXECUTEDBMS_AQ_BQVIEW EXECUTEQT52814_BUFFER SELECT Note that when queue table is created, a view called QT<nnn>_BUFFER is created in the SYS schema, and the queue table owner is given SELECT privileges on it. The <nnn> corresponds to the object_id of the associated queue table. SQL> select * from USER_ROLE_PRIVS;USERNAME GRANTED_ROLE ADM DEF OS_------------------------------ ------------------------------ ---- ---- ---AQ_USER1 AQ_ADMINISTRATOR_ROLE NO YES NOAQ_USER1 CONNECT NO YES NOAQ_USER1 RESOURCE NO YES NO It is good practice to configure central AQ administrative user. All admin and processing jobs are created, executed and administered as this user. This configuration is not mandatory however, and the database link can be owned by any existing queue user. If this latter configuration is used, ensure that the connecting user has the necessary privileges on the AQ packages and objects involved. Privileges for an AQ Administrative user Execute on DBMS_AQADM Execute on DBMS_AQ Granted the AQ_ADMINISTRATOR_ROLE Privileges for an AQ user Execute on DBMS_AQ Execute on the message payload Enqueue privileges on the remote queue Dequeue privileges on the originating queue Privileges need to be confirmed on both sites when propagation is scheduled to remote destinations. Verify that the user ID used to login to the destination through the database link has been granted privileges to use AQ. 5.2. Verify Queue Payload Types AQ will not propagate messages from one queue to another if the payload types of the two queues are not verified to be equivalent. An AQ administrator can verify if the source and destination's payload types match by executing the DBMS_AQADM.VERIFY_QUEUE_TYPES procedure. The results of the type checking will be stored in the SYS.AQ$_MESSAGE_TYPES table. This table can be accessed using the object identifier OID of the source queue and the address database link of the destination queue, i.e. [schema.]queue_name[@destination]. Prior to Oracle 9i the payload (message type) had to be the same for all the queue tables involved in propagation. From Oracle9i onwards a transformation can be used so that payloads can be converted from one type to another. The following procedural call made on the source database can verify whether we can propagate between the source and the destination queue tables. connect aq_user1/[email protected] serverout onDECLARErc_value number;BEGINDBMS_AQADM.VERIFY_QUEUE_TYPES(src_queue_name => 'AQ_USER1.Q_1', dest_queue_name => 'AQ_USER2.Q_2',destination => 'dbl_aq_user2.es',rc => rc_value);dbms_output.put_line('rc_value code is '||rc_value);END;/ If propagation is possible then the return code value will be 1. If it is 0 then propagation is not possible and further investigation of the types and transformations used by and in conjunction with the queue tables is required. With regard to comparison of the types the following sql can be used to extract the DDL for a specific type with' %' changed appropriately on the source and target. This can then be compared for the source and target. SET LONG 20000 set pagesize 50 EXECUTE DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM, 'STORAGE',false); SELECT DBMS_METADATA.GET_DDL('TYPE',t.type_name) from user_types t WHERE t.type_name like '%'; EXECUTE DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM, 'DEFAULT'); 5.3. Check Message State and Destination The first step in this process is to identify the queue table associated with the problem source queue. Although you schedule propagation for a specific queue, most of the meta-data associated with that queue is stored in the underlying queue table. The following statement finds the queue table for a given queue (note that this is a multiple-consumer queue table). SQL> select QUEUE_TABLE from DBA_QUEUES where NAME = 'MULTIPLEQ';QUEUE_TABLE --------------------MULTIPLEQTABLE For a small amount of messages in a multiple-consumer queue table, the following query can be run: SQL> select MSG_STATE, CONSUMER_NAME, ADDRESS from AQ$MULTIPLEQTABLE where QUEUE = 'MULTIPLEQ';MSG_STATE CONSUMER_NAME ADDRESS-------------- ----------------------- -------------READY AQUSER2 [email protected] AQUSER1READY AQUSER3 AQADM.INQ In this example we see 2 messages ready to be propagated to remote queues and 1 that is not. If the address column is blank, the message is not scheduled for propagation and can only be dequeued from the queue upon which it was enqueued. The MSG_STATE column values are discussed in Document 102330.1 Advanced Queueing MSG_STATE Values and their Interpretation. If the address column has a value, the message has been enqueued for propagation to another queue. The first row in the example includes a database link (@M2V102.ES). This demonstrates that the message should be propagated to a queue at a remote database. The third row does not include a database link so will be propagated to a queue that resides on the same database as the source queue. The consumer name is the intended recipient at the target queue. Note that we are not querying the base queue table directly; rather, we are querying a view that is available on top of every queue table, AQ$<queue_table_name>.A more realistic query in an environment where the queue table contains thousands of messages is8.0.3-compatible multiple-consumer queue table and all compatibility single-consumer queue tables select count(*), MSG_STATE, QUEUE from AQ$<queue_table_name>  group by MSG_STATE, QUEUE; 8.1.3 and 10.0-compatible queue tables select count(*), MSG_STATE, QUEUE, CONSUMER_NAME from AQ$<queue_table_name>group by MSG_STATE, QUEUE, CONSUMER_NAME; For multiple-consumer queue tables, if you did not see the expected CONSUMER_NAME , check the syntax of the enqueue code and verify the recipients are declared correctly. If a recipients list is not used on enqueue, check the subscriber list in the AQ$_<queue_table_name>_S view (note that a single-consumer queue table does not have a subscriber view. This view records all members of the default subscription list which were added using the DBMS_AQADM.ADD_SUBSCRIBER procedure and also those enqueued using a recipient list. SQL> select QUEUE, NAME, ADDRESS from AQ$MULTIPLEQTABLE_S;QUEUE NAME ADDRESS---------- ----------- -------------MULTIPLEQ AQUSER2 [email protected] AQUSER1 In this example we have 2 subscribers registered with the queue. We have a local subscriber AQUSER1, and a remote subscriber AQUSER2, on the queue INQ, owned by AQADM, at M2V102.ES. Unless overridden with a recipient list during enqueue every message enqueued to this queue will be propagated to INQ at M2V102.ES.For 8.1 style and above multiple consumer queue tables, you can also check the following information at the target: select CONSUMER_NAME, DEQ_TXN_ID, DEQ_TIME, DEQ_USER_ID, PROPAGATED_MSGID from AQ$<queue_table_name> where QUEUE = '<QUEUE_NAME>'; For 8.0 style queues, if the queue table supports multiple consumers you can obtain the same information from the history column of the queue table: select h.CONSUMER, h.TRANSACTION_ID, h.DEQ_TIME, h.DEQ_USER, h.PROPAGATED_MSGIDfrom AQ$<queue_table_name> t, table(t.history) h where t.Q_NAME = '<QUEUE_NAME>'; A non-NULL TRANSACTION_ID indicates that the message was successfully propagated. Further, the DEQ_TIME indicates the time of propagation, the DEQ_USER indicates the userid used for propagation, and the PROPAGATED_MSGID indicates the message ID of the message that was enqueued at the destination. 6. Additional Troubleshooting Steps for Propagation in an Oracle Streams Environment 6.1. Is the Propagation Enabled? For a propagation job to propagate messages, the propagation must be enabled. For Streams, a special view called DBA_PROPAGATION exists to convey information about Streams propagations. If messages are not being propagated by a propagation as expected, then the propagation might not be enabled. To query for this: SELECT p.PROPAGATION_NAME, DECODE(s.SCHEDULE_DISABLED, 'Y', 'Disabled','N', 'Enabled') SCHEDULE_DISABLED, s.PROCESS_NAME, s.FAILURES, s.LAST_ERROR_MSGFROM DBA_QUEUE_SCHEDULES s, DBA_PROPAGATION pWHERE p.DESTINATION_DBLINK = NVL(REGEXP_SUBSTR(s.DESTINATION, '[^@]+', 1, 2), s.DESTINATION) AND s.SCHEMA = p.SOURCE_QUEUE_OWNER AND s.QNAME = p.SOURCE_QUEUE_NAME AND MESSAGE_DELIVERY_MODE = 'PERSISTENT' order by PROPAGATION_NAME; At times, the propagation job may become "broken" or fail to start after an error has been encountered or after a database restart. If an error is indicated by the above query, an attempt to disable the propagation and then re-enable it can be made. In the examples below, for the propagation named STRMADMIN_PROPAGATE where the queue name is STREAMS_QUEUE owned by STRMADMIN and the destination database link is ORCL2.WORLD, the commands would be:10.2 and above exec dbms_propagation_adm.stop_propagation('STRMADMIN_PROPAGATE'); exec dbms_propagation_adm.start_propagation('STRMADMIN_PROPAGATE'); If the above does not fix the problem, stop the propagation specifying the force parameter (2nd parameter on stop_propagation) as TRUE: exec dbms_propagation_adm.stop_propagation('STRMADMIN_PROPAGATE',true); exec dbms_propagation_adm.start_propagation('STRMADMIN_PROPAGATE'); The statistics for the propagation as well as any old error messages are cleared when the force parameter is set to TRUE. Therefore if the propagation schedule is stopped with FORCE set to TRUE, and upon restart there is still an error message in DBA_PROPAGATION, then the error message is current.9.2 or 10.1 exec dbms_aqadm.disable_propagation_schedule('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); exec dbms.aqadm.enable_propagation_schedule('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); If the above does not fix the problem, perform an unschedule of propagation and then schedule_propagation: exec dbms_aqadm.unschedule_propagation('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); exec dbms_aqadm.schedule_propagation('STRMADMIN.STREAMS_QUEUE','ORCL2.WORLD'); Typically if the error from the first query in Section 6.1 recurs after restarting the propagation as shown above, further troubleshooting of the error is needed. 6.2. Check Propagation Rule Sets and Transformations Inspect the configuration of the rules in the rule set that is associated with the propagation process to make sure that they evaluate to TRUE as expected. If not, then the object or schema will not be propagated. Remember that when a negative rule evaluates to TRUE, the specified object or schema will not be propagated. Finally inspect any rule-based transformations that are implemented with propagation to make sure they are changing the data in the intended way.The following query shows what rule sets are assigned to a propagation: select PROPAGATION_NAME, RULE_SET_OWNER||'.'||RULE_SET_NAME "Positive Rule Set",NEGATIVE_RULE_SET_OWNER||'.'||NEGATIVE_RULE_SET_NAME "Negative Rule Set"from DBA_PROPAGATION; The next two queries list the propagation rules and their conditions. The first is for the positive rule set, the second is for the negative rule set: set long 4000select rsr.RULE_SET_OWNER||'.'||rsr.RULE_SET_NAME RULE_SET ,rsr.RULE_OWNER||'.'||rsr.RULE_NAME RULE_NAME,r.RULE_CONDITION CONDITION fromDBA_RULE_SET_RULES rsr, DBA_RULES rwhere rsr.RULE_NAME = r.RULE_NAME and rsr.RULE_OWNER = r.RULE_OWNER and RULE_SET_NAME in(select RULE_SET_NAME from DBA_PROPAGATION) order by rsr.RULE_SET_OWNER, rsr.RULE_SET_NAME;   set long 4000select c.PROPAGATION_NAME, rsr.RULE_SET_OWNER||'.'||rsr.RULE_SET_NAME RULE_SET ,rsr.RULE_OWNER||'.'||rsr.RULE_NAME RULE_NAME,r.RULE_CONDITION CONDITION fromDBA_RULE_SET_RULES rsr, DBA_RULES r ,DBA_PROPAGATION cwhere rsr.RULE_NAME = r.RULE_NAME and rsr.RULE_OWNER = r.RULE_OWNER andrsr.RULE_SET_OWNER=c.NEGATIVE_RULE_SET_OWNER and rsr.RULE_SET_NAME=c.NEGATIVE_RULE_SET_NAMEand rsr.RULE_SET_NAME in(select NEGATIVE_RULE_SET_NAME from DBA_PROPAGATION) order by rsr.RULE_SET_OWNER, rsr.RULE_SET_NAME; 6.3. Determining the Total Number of Messages and Bytes Propagated As in Section 3.1, determining if messages are flowing can be instructive to see whether the propagation is entirely hung or just slow. If the propagation is not in flow control (see Section 6.5.2), but the statistics are incrementing slowly, there may be a performance issue. For Streams implementations two views are available that can assist with this that can show the number of messages sent by a propagation, as well as the number of acknowledgements being returned from the target site: the V$PROPAGATION_SENDER view at the Source site and the V$PROPAGATION_RECEIVER view at the destination site. It is helpful to query both to determine if messages are being delivered to the target. Look for the statistics to increase.Source: select QUEUE_SCHEMA, QUEUE_NAME, DBLINK,HIGH_WATER_MARK, ACKNOWLEDGEMENT, TOTAL_MSGS, TOTAL_BYTESfrom V$PROPAGATION_SENDER; Target: select SRC_QUEUE_SCHEMA, SRC_QUEUE_NAME, SRC_DBNAME, DST_QUEUE_SCHEMA, DST_QUEUE_NAME, HIGH_WATER_MARK, ACKNOWLEDGEMENT, TOTAL_MSGS from V$PROPAGATION_RECEIVER; 6.4. Check Buffered Subscribers The V$BUFFERED_SUBSCRIBERS view displays information about subscribers for all buffered queues in the instance. This view can be queried to make sure that the site that the propagation is propagating to is listed as a subscriber address for the site being propagated from: select QUEUE_SCHEMA, QUEUE_NAME, SUBSCRIBER_ADDRESS from V$BUFFERED_SUBSCRIBERS; The SUBSCRIBER_ADDRESS column will not be populated when the propagation is local (between queues on the same database). 6.5. Common Streams Propagation Errors 6.5.1. ORA-02082: A loopback database link must have a connection qualifier. This error can occur if you use the Streams Setup Wizard in Oracle Enterprise Manager without first configuring the GLOBAL_NAME for your database. 6.5.2. ORA-25307: Enqueue rate too high. Enable flow control DBA_QUEUE_SCHEDULES will display this informational message for propagation when the automatic flow control (10g feature of Streams) has been invoked.Similar to Streams capture processes, a Streams propagation process can also go into a state of 'flow control. This is an informative message that indicates flow control has been automatically enabled to reduce the rate at which messages are being enqueued into at target queue.This typically occurs when the target site is unable to keep up with the rate of messages flowing from the source site. Other than checking that the apply process is running normally on the target site, usually no action is required by the DBA. Propagation and the capture process will be resumed automatically when the target site is able to accept more messages.The following document contains more information:Document 302109.1 Streams Propagation Error: ORA-25307 Enqueue rate too high. Enable flow controlSee the following document for one potential cause of this situation:Document 1097115.1 Oracle Streams Apply Reader is in 'Paused' State 6.5.3. ORA-25315 unsupported configuration for propagation of buffered messages This error typically occurs when the target database is RAC and usually indicates that an attempt was made to propagate buffered messages with the database link pointing to an instance in the destination database which is not the owner instance of the destination queue. To resolve the problem, use queue-to-queue propagation for buffered messages. 6.5.4. ORA-600 [KWQBMCRCPTS101] after dropping / recreating propagation For cause/fixes refer to:Document 421237.1 ORA-600 [KWQBMCRCPTS101] reported by a Qmon slave process after dropping a Streams Propagation 6.5.5. Stopping or Dropping a Streams Propagation Hangs See the following note:Document 1159787.1 Troubleshooting Streams Propagation When It is Not Functioning and Attempts to Stop It Hang 6.6. Streams Propagation-Related Notes for Common Issues Document 437838.1 Streams Specific PatchesDocument 749181.1 How to Recover Streams After Dropping PropagationDocument 368912.1 Queue to Queue Propagation Schedule encountered ORA-12514 in a RAC environmentDocument 564649.1 ORA-02068/ORA-03114/ORA-03113 Errors From Streams Propagation Process - Remote Database is Available and Unschedule/Reschedule Does Not ResolveDocument 553017.1 Stream Propagation Process Errors Ora-4052 Ora-6554 From 11g To 10201Document 944846.1 Streams Propagation Fails Ora-7445 [kohrsmc]Document 745601.1 ORA-23603 'STREAMS enqueue aborted due to low SGA' Error from Streams Propagation, and V$STREAMS_CAPTURE.STATE Hanging on 'Enqueuing Message'Document 333068.1 ORA-23603: Streams Enqueue Aborted Eue To Low SGADocument 363496.1 Ora-25315 Propagating on RAC StreamsDocument 368237.1 Unable to Unschedule Propagation. Streams Queue is InvalidDocument 436332.1 dbms_propagation_adm.stop_propagation hangsDocument 727389.1 Propagation Fails With ORA-12528Document 730911.1 ORA-4063 Is Reported After Dropping Negative Prop.RulesetDocument 460471.1 Propagation Blocked by Qmon Process - Streams_queue_table / 'library cache lock' waitsDocument 1165583.1 ORA-600 [kwqpuspse0-ack] In Streams EnvironmentDocument 1059029.1 Combined Capture and Apply (CCA) : Capture aborts : ORA-1422 after schedule_propagationDocument 556309.1 Changing Propagation/ queue_to_queue : false -> true does does not work; no LCRs propagatedDocument 839568.1 Propagation failing with error: ORA-01536: space quota exceeded for tablespace ''Document 311021.1 Streams Propagation Process : Ora 12154 After Reboot with Transparent Application Failover TAF configuredDocument 359971.1 STREAMS propagation to Primary of physical Standby configuation errors with Ora-01033, Ora-02068Document 1101616.1 DBMS_PROPAGATION_ADM.DROP_PROPAGATION FAILS WITH ORA-1747 7. Performance Issues A propagation may seem to be slow if the queries from Sections 3.1 and 6.3 show that the message statistics are not changing quickly. In Oracle Streams, this more usually is due to a slow apply process at the target rather than a slow propagation. Propagation could be inferred to be slow if the message statistics are changing, and the state of a capture process according to V$STREAMS_CAPTURE.STATE is PAUSED FOR FLOW CONTROL, but an ORA-25307 'Enqueue rate too high. Enable flow control' warning is NOT observed in DBA_QUEUE_SCHEDULES per Section 6.5.2. If this is the case, see the following notes / white papers for suggestions to increase performance:Document 335516.1 Master Note for Streams Performance RecommendationsDocument 730036.1 Overview for Troubleshooting Streams Performance IssuesDocument 780733.1 Streams Propagation Tuning with Network ParametersWhite Paper: http://www.oracle.com/technetwork/database/features/availability/maa-wp-10gr2-streams-performance-130059.pdfWhite Paper: Oracle Streams Configuration Best Practices: Oracle Database 10g Release 10.2, http://www.oracle.com/technetwork/database/features/availability/maa-10gr2-streams-configuration-132039.pdf, See APPENDIX A: USING STREAMS CONFIGURATIONS OVER A NETWORKFor basic AQ propagation, the network tuning in the aforementioned Appendix A of the white paper 'Oracle Streams Configuration Best Practices: Oracle Database 10g Release 10.2' is applicable. References NOTE:102330.1 - Advanced Queueing MSG_STATE Values and their InterpretationNOTE:102771.1 - Advanced Queueing Propagation using PL/SQLNOTE:1059029.1 - Combined Capture and Apply (CCA) : Capture aborts : ORA-1422 after schedule_propagationNOTE:1079577.1 - Advanced Queuing Propagation Fails With "ORA-22370: incorrect usage of method"NOTE:1083608.1 - 11g Streams and Oracle SchedulerNOTE:1087324.1 - ORA-01405 ORA-01422 reported by Adavanced Queueing Propagation schedules after RAC reconfigurationNOTE:1097115.1 - Oracle Streams Apply Reader is in 'Paused' StateNOTE:1101616.1 - DBMS_PROPAGATION_ADM.DROP_PROPAGATION FAILS WITH ORA-1747NOTE:1159787.1 - Troubleshooting Streams Propagation When It is Not Functioning and Attempts to Stop It HangNOTE:1165583.1 - ORA-600 [kwqpuspse0-ack] In Streams EnvironmentNOTE:118884.1 - How to unschedule a propagation schedule stuck in pending stateNOTE:1203544.1 - AQ PROPAGATION ABORTED WITH ORA-600[OCIKSIN: INVALID STATUS] ON SYS.DBMS_AQADM_SYS.AQ$_PROPAGATION_PROCEDURE AFTER UPGRADENOTE:1204080.1 - AQ Propagation Failing With ORA-25329 After Upgraded From 8i or 9i to 10g or 11g.NOTE:219416.1 - Advanced Queuing Propagation fails with ORA-22922NOTE:222992.1 - DBMS_AQADM.DISABLE_PROPAGATION_SCHEDULE Returns ORA-24082NOTE:253131.1 - Concurrent Writes May Corrupt LOB Segment When Using Auto Segment Space Management (ORA-1555)NOTE:282987.1 - Propagated Messages marked UNDELIVERABLE after Drop and Recreate Of Remote QueueNOTE:298015.1 - Kwqjswproc:Excep After Loop: Assigning To SelfNOTE:302109.1 - Streams Propagation Error: ORA-25307 Enqueue rate too high. Enable flow controlNOTE:311021.1 - Streams Propagation Process : Ora 12154 After Reboot with Transparent Application Failover TAF configuredNOTE:332792.1 - ORA-04061 error relating to SYS.DBMS_PRVTAQIP reported when setting up StatspackNOTE:333068.1 - ORA-23603: Streams Enqueue Aborted Eue To Low SGANOTE:335516.1 - Master Note for Streams Performance RecommendationsNOTE:353325.1 - ORA-24056: Internal inconsistency for QUEUE and destination NOTE:353754.1 - Streams Messaging Propagation Fails between Single and Multi-byte Charactersets when using Chararacter Length Semantics in the ADT.NOTE:359971.1 - STREAMS propagation to Primary of physical Standby configuation errors with Ora-01033, Ora-02068NOTE:363496.1 - Ora-25315 Propagating on RAC StreamsNOTE:365093.1 - ORA-07445 [kwqppay2aqe()+7360] reported on Propagation of a Transformed MessageNOTE:368237.1 - Unable to Unschedule Propagation. Streams Queue is InvalidNOTE:368912.1 - Queue to Queue Propagation Schedule encountered ORA-12514 in a RAC environmentNOTE:421237.1 - ORA-600 [KWQBMCRCPTS101] reported by a Qmon slave process after dropping a Streams PropagationNOTE:436332.1 - dbms_propagation_adm.stop_propagation hangsNOTE:437838.1 - Streams Specific PatchesNOTE:460471.1 - Propagation Blocked by Qmon Process - Streams_queue_table / 'library cache lock' waitsNOTE:463820.1 - Streams Combined Capture and Apply in 11gNOTE:553017.1 - Stream Propagation Process Errors Ora-4052 Ora-6554 From 11g To 10201NOTE:556309.1 - Changing Propagation/ queue_to_queue : false -> true does does not work; no LCRs propagatedNOTE:564649.1 - ORA-02068/ORA-03114/ORA-03113 Errors From Streams Propagation Process - Remote Database is Available and Unschedule/Reschedule Does Not ResolveNOTE:566622.1 - ORA-22275 when propagating >4K AQ$_JMS_TEXT_MESSAGEs from 9.2.0.8 to 10.2.0.1NOTE:727389.1 - Propagation Fails With ORA-12528NOTE:730036.1 - Overview for Troubleshooting Streams Performance IssuesNOTE:730911.1 - ORA-4063 Is Reported After Dropping Negative Prop.RulesetNOTE:731292.1 - ORA-25215 Reported On Local Propagation When Using Transformation with ANYDATA queue tablesNOTE:731539.1 - ORA-29268: HTTP client error 401 Unauthorized Error when the AQ Servlet attempts to Propagate a message via HTTPNOTE:745601.1 - ORA-23603 'STREAMS enqueue aborted due to low SGA' Error from Streams Propagation, and V$STREAMS_CAPTURE.STATE Hanging on 'Enqueuing Message'NOTE:749181.1 - How to Recover Streams After Dropping PropagationNOTE:780733.1 - Streams Propagation Tuning with Network ParametersNOTE:787367.1 - ORA-22275 reported on Propagating Messages with LOB component when propagating between 10.1 and 10.2NOTE:808136.1 - How to clear the old errors from DBA_PROPAGATION view ?NOTE:827184.1 - AQ Propagation with CLOB data types Fails with ORA-22990NOTE:827473.1 - How to alter propagation from queue_to_queue to queue_to_dblinkNOTE:839568.1 - Propagation failing with error: ORA-01536: space quota exceeded for tablespace ''NOTE:846297.1 - AQ Propagation Fails : ORA-00600[kope2upic2954] or Ora-00600[Kghsstream_copyn]NOTE:944846.1 - Streams Propagation Fails Ora-7445 [kohrsmc]

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  • Issue with dynamic array Queue data structure with void pointer

    - by Nazgulled
    Hi, Maybe there's no way to solve this the way I'd like it but I don't know everything so I better ask... I've implemented a simple Queue with a dynamic array so the user can initialize with whatever number of items it wants. I'm also trying to use a void pointer as to allow any data type, but that's the problem. Here's my code: typedef void * QueueValue; typedef struct sQueueItem { QueueValue value; } QueueItem; typedef struct sQueue { QueueItem *items; int first; int last; int size; int count; } Queue; void queueInitialize(Queue **queue, size_t size) { *queue = xmalloc(sizeof(Queue)); QueueItem *items = xmalloc(sizeof(QueueItem) * size); (*queue)->items = items; (*queue)->first = 0; (*queue)->last = 0; (*queue)->size = size; (*queue)->count = 0; } Bool queuePush(Queue * const queue, QueueValue value, size_t val_sz) { if(isNull(queue) || isFull(queue)) return FALSE; queue->items[queue->last].value = xmalloc(val_sz); memcpy(queue->items[queue->last].value, value, val_sz); queue->last = (queue->last+1) % queue->size; queue->count += 1; return TRUE; } Bool queuePop(Queue * const queue, QueueValue *value) { if(isEmpty(queue)) return FALSE; *value = queue->items[queue->first].value; free(queue->items[queue->first].value); queue->first = (queue->first+1) % queue->size; queue->count -= 1; return TRUE; } The problem lies on the queuePop function. When I call it, I lose the value because I free it right away. I can't seem to solve this dilemma. I want my library to be generic and modular. The user should not care about allocating and freeing memory, that's the library's job. How can the user still get the value from queuePop and let the library handle all memory allocs/frees?

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  • priority queue with limited space: looking for a good algorithm

    - by SigTerm
    This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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  • c++ queue template

    - by Dalton Conley
    ALright, pardon my messy code please. Below is my queue class. #include <iostream> using namespace std; #ifndef QUEUE #define QUEUE /*---------------------------------------------------------------------------- Student Class # Methods # Student() // default constructor Student(string, int) // constructor display() // out puts a student # Data Members # Name // string name Id // int id ----------------------------------------------------------------------------*/ class Student { public: Student() { } Student(string iname, int iid) { name = iname; id = iid; } void display(ostream &out) const { out << "Student Name: " << name << "\tStudent Id: " << id << "\tAddress: " << this << endl; } private: string name; int id; }; // define a typedef of a pointer to a student. typedef Student * StudentPointer; template <typename T> class Queue { public: /*------------------------------------------------------------------------ Queue Default Constructor Preconditions: none Postconditions: assigns default values for front and back to 0 description: constructs a default empty Queue. ------------------------------------------------------------------------*/ Queue() : myFront(0), myBack(0) {} /*------------------------------------------------------------------------ Copy Constructor Preconditions: requres a reference to a value for which you are copying Postconditions: assigns a copy to the parent Queue. description: Copys a queue and assigns it to the parent Queue. ------------------------------------------------------------------------*/ Queue(const T & q) { myFront = myBack = 0; if(!q.empty()) { // copy the first node myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } /*------------------------------------------------------------------------ Destructor Preconditions: none Postconditions: deallocates the dynamic memory for the Queue description: deletes the memory stored for a Queue. ------------------------------------------------------------------------*/ ~Queue() { NodePointer prev = myFront, ptr; while(prev != NULL) { ptr = prev->next; delete prev; prev = ptr; } } /*------------------------------------------------------------------------ Empty() Preconditions: none Postconditions: returns a boolean value. description: returns true/false based on if the queue is empty or full. ------------------------------------------------------------------------*/ bool empty() const { return (myFront == NULL); } /*------------------------------------------------------------------------ Enqueue Preconditions: requires a constant reference Postconditions: allocates memory and appends a value at the end of a queue description: ------------------------------------------------------------------------*/ void enqueue(const T & value) { NodePointer newNodePtr = new Node(value); if(empty()) { myFront = myBack = newNodePtr; newNodePtr->next = NULL; } else { myBack->next = newNodePtr; myBack = newNodePtr; newNodePtr->next = NULL; } } /*------------------------------------------------------------------------ Display Preconditions: requires a reference of type ostream Postconditions: returns the ostream value (for chaining) description: outputs the contents of a queue. ------------------------------------------------------------------------*/ void display(ostream & out) const { NodePointer ptr; ptr = myFront; while(ptr != NULL) { out << ptr->data << " "; ptr = ptr->next; } out << endl; } /*------------------------------------------------------------------------ Front Preconditions: none Postconditions: returns a value of type T description: returns the first value in the parent Queue. ------------------------------------------------------------------------*/ T front() const { if ( !empty() ) return (myFront->data); else { cerr << "*** Queue is empty -- returning garbage value ***\n"; T * temp = new(T); T garbage = * temp; delete temp; return garbage; } } /*------------------------------------------------------------------------ Dequeue Preconditions: none Postconditions: removes the first value in a queue ------------------------------------------------------------------------*/ void dequeue() { if ( !empty() ) { NodePointer ptr = myFront; myFront = myFront->next; delete ptr; if(myFront == NULL) myBack = NULL; } else { cerr << "*** Queue is empty -- " "can't remove a value ***\n"; exit(1); } } /*------------------------------------------------------------------------ pverloaded = operator Preconditions: requires a constant reference Postconditions: returns a const type T description: this allows assigning of queues to queues ------------------------------------------------------------------------*/ Queue<T> & operator=(const T &q) { // make sure we arent reassigning ourself // e.g. thisQueue = thisQueue. if(this != &q) { this->~Queue(); if(q.empty()) { myFront = myBack = NULL; } else { myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } return *this; } private: class Node { public: T data; Node * next; Node(T value, Node * first = 0) : data(value), next(first) {} }; typedef Node * NodePointer; NodePointer myFront, myBack, queueSize; }; /*------------------------------------------------------------------------ join Preconditions: requires 2 queue values Postconditions: appends queue2 to the end of queue1 description: this function joins 2 queues into 1. ------------------------------------------------------------------------*/ template <typename T> Queue<T> join(Queue<T> q1, Queue<T> q2) { Queue<T> q1Copy(q1), q2Copy(q2); Queue<T> jQueue; while(!q1Copy.empty()) { jQueue.enqueue(q1Copy.front()); q1Copy.dequeue(); } while(!q2Copy.empty()) { jQueue.enqueue(q2Copy.front()); q2Copy.dequeue(); } cout << jQueue << endl; return jQueue; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a Queue of type T Postconditions: returns the ostream (for chaining) description: this function is overloaded for outputing a queue with << ----------------------------------------------------------------------------*/ template <typename T> ostream & operator<<(ostream &out, Queue<T> &s) { s.display(out); return out; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of type Student Postconditions: none description: this function is overloaded for outputing an object of type Student. ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, Student &s) { s.display(out); } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of a pointer to a Student object. Postconditions: none description: this function is overloaded for outputing pointers to Students ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, StudentPointer &s) { s->display(out); } #endif Now I'm having some issues with it. For one, when I add 0 to a queue and then I output the queue like so.. Queue<double> qdub; qdub.enqueue(0); cout << qdub << endl; That works, it will output 0. But for example, if I modify that queue in any way.. like.. assign it to a different queue.. Queue<double> qdub1; Queue<double> qdub2; qdub1.enqueue(0; qdub2 = qdub1; cout << qdub2 << endl; It will give me weird values for 0 like.. 7.86914e-316. Help on this would be much appreciated!

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  • Windows Azure AppFabric: ServiceBus Queue WPF Sample

    - by xamlnotes
    The latest version of the AppFabric ServiceBus now has support for queues and topics. Today I will show you a bit about using queues and also talk about some of the best practices in using them. If you are just getting started, you can check out this site for more info on Windows Azure. One of the 1st things I thought if when Azure was announced back when was how we handle fault tolerance. Web sites hosted in Azure are no much of an issue unless they are using SQL Azure and then you must account for potential fault or latency issues. Today I want to talk a bit about ServiceBus and how to handle fault tolerance.  And theres stuff like connecting to the servicebus and so on you have to take care of. To demonstrate some of the things you can do, let me walk through this sample WPF app that I am posting for you to download. To start off, the application is going to need things like the servicenamespace, issuer details and so forth to make everything work.  To facilitate this I created settings in the wpf app for all of these items. Then I mapped a static class to them and set the values when the program loads like so: StaticElements.ServiceNamespace = Convert.ToString(Properties.Settings.Default["ServiceNamespace"]); StaticElements.IssuerName = Convert.ToString(Properties.Settings.Default["IssuerName"]); StaticElements.IssuerKey = Convert.ToString(Properties.Settings.Default["IssuerKey"]); StaticElements.QueueName = Convert.ToString(Properties.Settings.Default["QueueName"]);   Now I can get to each of these elements plus some other common values or instances directly from the StaticElements class. Now, lets look at the application.  The application looks like this when it starts:   The blue graphic represents the queue we are going to use.  The next figure shows the form after items were added and the queue stats were updated . You can see how the queue has grown: To add an item to the queue, click the Add Order button which displays the following dialog: After you fill in the form and press OK, the order is published to the ServiceBus queue and the form closes. The application also allows you to read the queued items by clicking the Process Orders button. As you can see below, the form shows the queued items in a list and the  queue has disappeared as its now empty. In real practice we normally would use a Windows Service or some other automated process to subscribe to the queue and pull items from it. I created a class named ServiceBusQueueHelper that has the core queue features we need. There are three public methods: * GetOrCreateQueue – Gets an instance of the queue description if the queue exists. if not, it creates the queue and returns a description instance. * SendMessageToQueue = This method takes an order instance and sends it to the queue. The call to the queue is wrapped in the ExecuteAction method from the Transient Fault Tolerance Framework and handles all the retry logic for the queue send process. * GetOrderFromQueue – Grabs an order from the queue and returns a typed order from the queue. It also marks the message complete so the queue can remove it.   Now lets turn to the WPF window code (MainWindow.xaml.cs). The constructor contains the 4 lines shown about to setup the static variables and to perform other initialization tasks. The next few lines setup certain features we need for the ServiceBus: TokenProvider credentials = TokenProvider.CreateSharedSecretTokenProvider(StaticElements.IssuerName, StaticElements.IssuerKey); Uri serviceUri = ServiceBusEnvironment.CreateServiceUri("sb", StaticElements.ServiceNamespace, string.Empty); StaticElements.CurrentNamespaceManager = new NamespaceManager(serviceUri, credentials); StaticElements.CurrentMessagingFactory = MessagingFactory.Create(serviceUri, credentials); The next two lines update the queue name label and also set the timer to 20 seconds.             QueueNameLabel.Content = StaticElements.QueueName;             _timer.Interval = TimeSpan.FromSeconds(20);             Next I call the UpdateQueueStats to initialize the UI for the queue:             UpdateQueueStats();             _timer.Tick += new EventHandler(delegate(object s, EventArgs a)                         {                      UpdateQueueStats();                  });             _timer.Start();         } The UpdateQueueStats method shown below. You can see that it uses the GetOrCreateQueue method mentioned earlier to grab the queue description, then it can get the MessageCount property.         private void UpdateQueueStats()         {             _queueDescription = _serviceBusQueueHelper.GetOrCreateQueue();             QueueCountLabel.Content = "(" + _queueDescription.MessageCount + ")";             long count = _queueDescription.MessageCount;             long queueWidth = count * 20;             QueueRectangle.Width = queueWidth;             QueueTickCount += 1;             TickCountlabel.Content = QueueTickCount.ToString();         }   The ReadQueueItemsButton_Click event handler calls the GetOrderFromQueue method and adds the order to the listbox. If you look at the SendQueueMessageController, you can see the SendMessage method that sends an order to the queue. Its pretty simple as it just creates a new CustomerOrderEntity instance,fills it and then passes it to the SendMessageToQueue. As you can see, all of our interaction with the queue is done through the helper class (ServiceBusQueueHelper). Now lets dig into the helper class. First, before you create anything like this, download the Transient Fault Handling Framework. Microsoft provides this free and they also provide the C# source. Theres a great article that shows how to use this framework with ServiceBus. I included the entire ServiceBusQueueHelper class in List 1. Notice the using statements for TransientFaultHandling: using Microsoft.AzureCAT.Samples.TransientFaultHandling; using Microsoft.AzureCAT.Samples.TransientFaultHandling.ServiceBus; The SendMessageToQueue in Listing 1 shows how to use the async send features of ServiceBus with them wrapped in the Transient Fault Handling Framework.  It is not much different than plain old ServiceBus calls but it sure makes it easy to have the fault tolerance added almost for free. The GetOrderFromQueue uses the standard synchronous methods to access the queue. The best practices article walks through using the async approach for a receive operation also.  Notice that this method makes a call to Receive to get the message then makes a call to GetBody to get a new strongly typed instance of CustomerOrderEntity to return. Listing 1 using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.AzureCAT.Samples.TransientFaultHandling; using Microsoft.AzureCAT.Samples.TransientFaultHandling.ServiceBus; using Microsoft.ServiceBus; using Microsoft.ServiceBus.Messaging; using System.Xml.Serialization; using System.Diagnostics; namespace WPFServicebusPublishSubscribeSample {     class ServiceBusQueueHelper     {         RetryPolicy currentPolicy = new RetryPolicy<ServiceBusTransientErrorDetectionStrategy>(RetryPolicy.DefaultClientRetryCount);         QueueClient currentQueueClient;         public QueueDescription GetOrCreateQueue()         {                        QueueDescription queue = null;             bool createNew = false;             try             {                 // First, let's see if a queue with the specified name already exists.                 queue = currentPolicy.ExecuteAction<QueueDescription>(() => { return StaticElements.CurrentNamespaceManager.GetQueue(StaticElements.QueueName); });                 createNew = (queue == null);             }             catch (MessagingEntityNotFoundException)             {                 // Looks like the queue does not exist. We should create a new one.                 createNew = true;             }             // If a queue with the specified name doesn't exist, it will be auto-created.             if (createNew)             {                 try                 {                     var newqueue = new QueueDescription(StaticElements.QueueName);                     queue = currentPolicy.ExecuteAction<QueueDescription>(() => { return StaticElements.CurrentNamespaceManager.CreateQueue(newqueue); });                 }                 catch (MessagingEntityAlreadyExistsException)                 {                     // A queue under the same name was already created by someone else,                     // perhaps by another instance. Let's just use it.                     queue = currentPolicy.ExecuteAction<QueueDescription>(() => { return StaticElements.CurrentNamespaceManager.GetQueue(StaticElements.QueueName); });                 }             }             currentQueueClient = StaticElements.CurrentMessagingFactory.CreateQueueClient(StaticElements.QueueName);             return queue;         }         public void SendMessageToQueue(CustomerOrderEntity Order)         {             BrokeredMessage msg = null;             GetOrCreateQueue();             // Use a retry policy to execute the Send action in an asynchronous and reliable fashion.             currentPolicy.ExecuteAction             (                 (cb) =>                 {                     // A new BrokeredMessage instance must be created each time we send it. Reusing the original BrokeredMessage instance may not                     // work as the state of its BodyStream cannot be guaranteed to be readable from the beginning.                     msg = new BrokeredMessage(Order);                     // Send the event asynchronously.                     currentQueueClient.BeginSend(msg, cb, null);                 },                 (ar) =>                 {                     try                     {                         // Complete the asynchronous operation.                         // This may throw an exception that will be handled internally by the retry policy.                         currentQueueClient.EndSend(ar);                     }                     finally                     {                         // Ensure that any resources allocated by a BrokeredMessage instance are released.                         if (msg != null)                         {                             msg.Dispose();                             msg = null;                         }                     }                 },                 (ex) =>                 {                     // Always dispose the BrokeredMessage instance even if the send                     // operation has completed unsuccessfully.                     if (msg != null)                     {                         msg.Dispose();                         msg = null;                     }                     // Always log exceptions.                     Trace.TraceError(ex.Message);                 }             );         }                 public CustomerOrderEntity GetOrderFromQueue()         {             CustomerOrderEntity Order = new CustomerOrderEntity();             QueueClient myQueueClient = StaticElements.CurrentMessagingFactory.CreateQueueClient(StaticElements.QueueName, ReceiveMode.PeekLock);             BrokeredMessage message;             ServiceBusQueueHelper serviceBusQueueHelper = new ServiceBusQueueHelper();             QueueDescription queueDescription;             queueDescription = serviceBusQueueHelper.GetOrCreateQueue();             if (queueDescription.MessageCount > 0)             {                 message = myQueueClient.Receive(TimeSpan.FromSeconds(90));                 if (message != null)                 {                     try                     {                         Order = message.GetBody<CustomerOrderEntity>();                         message.Complete();                     }                     catch (Exception ex)                     {                         throw ex;                     }                 }                 else                 {                     throw new Exception("Did not receive the messages");                 }             }             return Order;         }     } } I will post a link to the download demo in a separate post soon.

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  • JMS Step 3 - Using the QueueReceive.java Sample Program to Read a Message from a JMS Queue

    - by John-Brown.Evans
    JMS Step 3 - Using the QueueReceive.java Sample Program to Read a Message from a JMS Queue ol{margin:0;padding:0} .c18_3{vertical-align:top;width:487.3pt;border-style:solid;background-color:#f3f3f3;border-color:#000000;border-width:1pt;padding:0pt 5pt 0pt 5pt} .c20_3{vertical-align:top;width:487.3pt;border-style:solid;border-color:#ffffff;border-width:1pt;padding:5pt 5pt 5pt 5pt} .c19_3{background-color:#ffffff} .c17_3{list-style-type:circle;margin:0;padding:0} .c12_3{list-style-type:disc;margin:0;padding:0} .c6_3{font-style:italic;font-weight:bold} .c10_3{color:inherit;text-decoration:inherit} .c1_3{font-size:10pt;font-family:"Courier New"} .c2_3{line-height:1.0;direction:ltr} .c9_3{padding-left:0pt;margin-left:72pt} .c15_3{padding-left:0pt;margin-left:36pt} .c3_3{color:#1155cc;text-decoration:underline} .c5_3{height:11pt} .c14_3{border-collapse:collapse} .c7_3{font-family:"Courier New"} .c0_3{background-color:#ffff00} .c16_3{font-size:18pt} .c8_3{font-weight:bold} .c11_3{font-size:24pt} .c13_3{font-style:italic} .c4_3{direction:ltr} .title{padding-top:24pt;line-height:1.15;text-align:left;color:#000000;font-size:36pt;font-family:"Arial";font-weight:bold;padding-bottom:6pt}.subtitle{padding-top:18pt;line-height:1.15;text-align:left;color:#666666;font-style:italic;font-size:24pt;font-family:"Georgia";padding-bottom:4pt} li{color:#000000;font-size:10pt;font-family:"Arial"} p{color:#000000;font-size:10pt;margin:0;font-family:"Arial"} h1{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:24pt;font-family:"Arial";font-weight:normal} h2{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:18pt;font-family:"Arial";font-weight:normal} h3{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:14pt;font-family:"Arial";font-weight:normal} h4{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:12pt;font-family:"Arial";font-weight:normal} h5{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:11pt;font-family:"Arial";font-weight:normal} h6{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:10pt;font-family:"Arial";font-weight:normal} This post continues the series of JMS articles which demonstrate how to use JMS queues in a SOA context. In the first post, JMS Step 1 - How to Create a Simple JMS Queue in Weblogic Server 11g we looked at how to create a JMS queue and its dependent objects in WebLogic Server. In the previous post, JMS Step 2 - Using the QueueSend.java Sample Program to Send a Message to a JMS Queue I showed how to write a message to that JMS queue using the QueueSend.java sample program. In this article, we will use a similar sample, the QueueReceive.java program to read the message from that queue. Please review the previous posts if you have not already done so, as they contain prerequisites for executing the sample in this article. 1. Source code The following java code will be used to read the message(s) from the JMS queue. As with the previous example, it is based on a sample program shipped with the WebLogic Server installation. The sample is not installed by default, but needs to be installed manually using the WebLogic Server Custom Installation option, together with many, other useful samples. You can either copy-paste the following code into your editor, or install all the samples. The knowledge base article in My Oracle Support: How To Install WebLogic Server and JMS Samples in WLS 10.3.x (Doc ID 1499719.1) describes how to install the samples. QueueReceive.java package examples.jms.queue; import java.util.Hashtable; import javax.jms.*; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; /** * This example shows how to establish a connection to * and receive messages from a JMS queue. The classes in this * package operate on the same JMS queue. Run the classes together to * witness messages being sent and received, and to browse the queue * for messages. This class is used to receive and remove messages * from the queue. * * @author Copyright (c) 1999-2005 by BEA Systems, Inc. All Rights Reserved. */ public class QueueReceive implements MessageListener { // Defines the JNDI context factory. public final static String JNDI_FACTORY="weblogic.jndi.WLInitialContextFactory"; // Defines the JMS connection factory for the queue. public final static String JMS_FACTORY="jms/TestConnectionFactory"; // Defines the queue. public final static String QUEUE="jms/TestJMSQueue"; private QueueConnectionFactory qconFactory; private QueueConnection qcon; private QueueSession qsession; private QueueReceiver qreceiver; private Queue queue; private boolean quit = false; /** * Message listener interface. * @param msg message */ public void onMessage(Message msg) { try { String msgText; if (msg instanceof TextMessage) { msgText = ((TextMessage)msg).getText(); } else { msgText = msg.toString(); } System.out.println("Message Received: "+ msgText ); if (msgText.equalsIgnoreCase("quit")) { synchronized(this) { quit = true; this.notifyAll(); // Notify main thread to quit } } } catch (JMSException jmse) { System.err.println("An exception occurred: "+jmse.getMessage()); } } /** * Creates all the necessary objects for receiving * messages from a JMS queue. * * @param ctx JNDI initial context * @param queueName name of queue * @exception NamingException if operation cannot be performed * @exception JMSException if JMS fails to initialize due to internal error */ public void init(Context ctx, String queueName) throws NamingException, JMSException { qconFactory = (QueueConnectionFactory) ctx.lookup(JMS_FACTORY); qcon = qconFactory.createQueueConnection(); qsession = qcon.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); queue = (Queue) ctx.lookup(queueName); qreceiver = qsession.createReceiver(queue); qreceiver.setMessageListener(this); qcon.start(); } /** * Closes JMS objects. * @exception JMSException if JMS fails to close objects due to internal error */ public void close()throws JMSException { qreceiver.close(); qsession.close(); qcon.close(); } /** * main() method. * * @param args WebLogic Server URL * @exception Exception if execution fails */ public static void main(String[] args) throws Exception { if (args.length != 1) { System.out.println("Usage: java examples.jms.queue.QueueReceive WebLogicURL"); return; } InitialContext ic = getInitialContext(args[0]); QueueReceive qr = new QueueReceive(); qr.init(ic, QUEUE); System.out.println( "JMS Ready To Receive Messages (To quit, send a \"quit\" message)."); // Wait until a "quit" message has been received. synchronized(qr) { while (! qr.quit) { try { qr.wait(); } catch (InterruptedException ie) {} } } qr.close(); } private static InitialContext getInitialContext(String url) throws NamingException { Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, JNDI_FACTORY); env.put(Context.PROVIDER_URL, url); return new InitialContext(env); } } 2. How to Use This Class 2.1 From the file system on Linux This section describes how to use the class from the file system of a WebLogic Server installation. Log in to a machine with a WebLogic Server installation and create a directory to contain the source and code matching the package name, e.g. span$HOME/examples/jms/queue. Copy the above QueueReceive.java file to this directory. Set the CLASSPATH and environment to match the WebLogic server environment. Go to $MIDDLEWARE_HOME/user_projects/domains/base_domain/bin  and execute . ./setDomainEnv.sh Collect the following information required to run the script: The JNDI name of the JMS queue to use In the WebLogic server console > Services > Messaging > JMS Modules > Module name, (e.g. TestJMSModule) > JMS queue name, (e.g. TestJMSQueue) select the queue and note its JNDI name, e.g. jms/TestJMSQueue The JNDI name of the connection factory to use to connect to the queue Follow the same path as above to get the connection factory for the above queue, e.g. TestConnectionFactory and its JNDI name e.g. jms/TestConnectionFactory The URL and port of the WebLogic server running the above queue Check the JMS server for the above queue and the managed server it is targeted to, for example soa_server1. Now find the port this managed server is listening on, by looking at its entry under Environment > Servers in the WLS console, e.g. 8001 The URL for the server to be passed to the QueueReceive program will therefore be t3://host.domain:8001 e.g. t3://jbevans-lx.de.oracle.com:8001 Edit Queue Receive .java and enter the above queue name and connection factory respectively under ... public final static String JMS_FACTORY="jms/TestConnectionFactory"; ... public final static String QUEUE="jms/TestJMSQueue"; ... Compile Queue Receive .java using javac Queue Receive .java Go to the source’s top-level directory and execute it using java examples.jms.queue.Queue Receive   t3://jbevans-lx.de.oracle.com:8001 This will print a message that it is ready to receive messages or to send a “quit” message to end. The program will read all messages in the queue and print them to the standard output until it receives a message with the payload “quit”. 2.2 From JDeveloper The steps from JDeveloper are the same as those used for the previous program QueueSend.java, which is used to send a message to the queue. So we won't repeat them here. Please see the previous blog post at JMS Step 2 - Using the QueueSend.java Sample Program to Send a Message to a JMS Queue and apply the same steps in that example to the QueueReceive.java program. This concludes the example. In the following post we will create a BPEL process which writes a message based on an XML schema to the queue.

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  • Exim queue in WHM

    - by Xobb
    Hi fellas, I've got the centos server with WHM. The mail server is exim. I need exim put all messages in queue and not sending directly.Though I've added the queue_only option to exim configuration and the messages are collected in the queue now. Afterwards I've found out that someone is calling exim -q to process the queue every once in a while. I've found the following cron job: 0 6 * * * /scripts/exim_tidydb > /dev/null 2>&1 which I beleive has been used to process the exim queue. Also I suspect that script was installed alongside with WHM. Surely I've commented it out and was expecting everything to work just fine. But that didn't happen. I still get the exim queue processed once in a while. Am I missing anything? What may cause my exim queue to process? Here is cat /etc/exim.conf | grep queue queue_only deliver_queue_load_max = 3 Thanks

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  • SQLite as an App Queue, Exclusive Row Lock?

    - by ScSub
    I am considering using SQLite as a "job queue container", and was wondering how I could do so, using custom C# (with ADO.NET) to work the database. If this was SQL Server, I would setup a serializable transaction to make sure the parent row and child rows were exclusively mine until I was done. I'm not sure how that would work in SQLite, can anyone offer any assistance? Or if there are any other existing implementations of message queueing with SQLite, I'd appreciate any pointers in that direction as well. Thanks!

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  • FreeBSD Listen Queue Overflows - can't increase max queue size

    - by Harry
    I have a decently high trafficked FreeBSD Nginx server, and I'm starting to get a large number of listen queue overflows: [root@svr ~]# netstat -sp tcp | fgrep listen 80361931 listen queue overflows [root@svr ~]# netstat -Lan | grep "*.80" tcp4 192/0/128 *.80 [root@svr ~]# sysctl kern.ipc.somaxconn kern.ipc.somaxconn: 12288 [root@svr ~]# However I can't seem to increase the max listen queue length past 128. I've increased kern.ipc.somaxconn, but it's not changing the max. Am I missing something? Thanks!

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  • Message Queue: Which one is the best scenario?

    - by pandaforme
    I write a web crawler. The crawler has 2 steps: get a html page then parse the page I want to use message queue to improve performance and throughput. I think 2 scenarios: scenario 1: structure: urlProducer -> queue1 -> urlConsumer -> queue2 -> parserConsumer urlProducer: get a target url and add it to queue1 urlConsumer: according to the job info, get the html page and add it to queue2 parserConsumer: according to the job info, parse the page scenario 2: structure: urlProducer -> queue1 -> urlConsumer parserProducer-> queue2 -> parserConsumer urlProducer : get a target url and add it to queue1 urlConsumer: according to the job info, get the html page and write it to db parserProducer: get the html page from db and add it to queue2 parserConsumer: according to the job info, parse the page There are multiple producers or consumers in each structure. scenario1 likes a chaining call. It's difficult to find the point of problem, when occurring errors. scenario2 decouples queue1 and queue2. It's easy to find the point of problem, when occurring errors. I'm not sure the notion is correct. Which one is the best scenario? Or other scenarios? Thanks~

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  • JMS Step 2 - Using the QueueSend.java Sample Program to Send a Message to a JMS Queue

    - by John-Brown.Evans
    JMS Step 2 - Using the QueueSend.java Sample Program to Send a Message to a JMS Queue .c21_2{vertical-align:top;width:487.3pt;border-style:solid;border-color:#000000;border-width:1pt;padding:5pt 5pt 5pt 5pt} .c15_2{vertical-align:top;width:487.3pt;border-style:solid;border-color:#ffffff;border-width:1pt;padding:5pt 5pt 5pt 5pt} .c0_2{padding-left:0pt;direction:ltr;margin-left:36pt} .c20_2{list-style-type:circle;margin:0;padding:0} .c10_2{list-style-type:disc;margin:0;padding:0} .c6_2{background-color:#ffffff} .c17_2{padding-left:0pt;margin-left:72pt} .c3_2{line-height:1.0;direction:ltr} .c1_2{font-size:10pt;font-family:"Courier New"} .c16_2{color:#1155cc;text-decoration:underline} .c13_2{color:inherit;text-decoration:inherit} .c7_2{background-color:#ffff00} .c9_2{border-collapse:collapse} .c2_2{font-family:"Courier New"} .c18_2{font-size:18pt} .c5_2{font-weight:bold} .c19_2{color:#ff0000} .c12_2{background-color:#f3f3f3;border-style:solid;border-color:#000000;border-width:1pt;} .c14_2{font-size:24pt} .c8_2{direction:ltr;background-color:#ffffff} .c11_2{font-style:italic} .c4_2{height:11pt} .title{padding-top:24pt;line-height:1.15;text-align:left;color:#000000;font-size:36pt;font-family:"Arial";font-weight:bold;padding-bottom:6pt}.subtitle{padding-top:18pt;line-height:1.15;text-align:left;color:#666666;font-style:italic;font-size:24pt;font-family:"Georgia";padding-bottom:4pt} li{color:#000000;font-size:10pt;font-family:"Arial"} p{color:#000000;font-size:10pt;margin:0;font-family:"Arial"} h1{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:24pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h2{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:18pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h3{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:14pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h4{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:12pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h5{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:11pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h6{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:10pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} This post is the second in a series of JMS articles which demonstrate how to use JMS queues in a SOA context. In the previous post JMS Step 1 - How to Create a Simple JMS Queue in Weblogic Server 11g I showed you how to create a JMS queue and its dependent objects in WebLogic Server. In this article, we will use a sample program to write a message to that queue. Please review the previous post if you have not created those objects yet, as they will be required later in this example. The previous post also includes useful background information and links to the Oracle documentation for addional research. The following post in this series will show how to read the message from the queue again. 1. Source code The following java code will be used to write a message to the JMS queue. It is based on a sample program provided with the WebLogic Server installation. The sample is not installed by default, but needs to be installed manually using the WebLogic Server Custom Installation option, together with many, other useful samples. You can either copy-paste the following code into your editor, or install all the samples. The knowledge base article in My Oracle Support: How To Install WebLogic Server and JMS Samples in WLS 10.3.x (Doc ID 1499719.1) describes how to install the samples. QueueSend.java package examples.jms.queue; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Hashtable; import javax.jms.*; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; /** This example shows how to establish a connection * and send messages to the JMS queue. The classes in this * package operate on the same JMS queue. Run the classes together to * witness messages being sent and received, and to browse the queue * for messages. The class is used to send messages to the queue. * * @author Copyright (c) 1999-2005 by BEA Systems, Inc. All Rights Reserved. */ public class QueueSend { // Defines the JNDI context factory. public final static String JNDI_FACTORY="weblogic.jndi.WLInitialContextFactory"; // Defines the JMS context factory. public final static String JMS_FACTORY="jms/TestConnectionFactory"; // Defines the queue. public final static String QUEUE="jms/TestJMSQueue"; private QueueConnectionFactory qconFactory; private QueueConnection qcon; private QueueSession qsession; private QueueSender qsender; private Queue queue; private TextMessage msg; /** * Creates all the necessary objects for sending * messages to a JMS queue. * * @param ctx JNDI initial context * @param queueName name of queue * @exception NamingException if operation cannot be performed * @exception JMSException if JMS fails to initialize due to internal error */ public void init(Context ctx, String queueName) throws NamingException, JMSException { qconFactory = (QueueConnectionFactory) ctx.lookup(JMS_FACTORY); qcon = qconFactory.createQueueConnection(); qsession = qcon.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); queue = (Queue) ctx.lookup(queueName); qsender = qsession.createSender(queue); msg = qsession.createTextMessage(); qcon.start(); } /** * Sends a message to a JMS queue. * * @param message message to be sent * @exception JMSException if JMS fails to send message due to internal error */ public void send(String message) throws JMSException { msg.setText(message); qsender.send(msg); } /** * Closes JMS objects. * @exception JMSException if JMS fails to close objects due to internal error */ public void close() throws JMSException { qsender.close(); qsession.close(); qcon.close(); } /** main() method. * * @param args WebLogic Server URL * @exception Exception if operation fails */ public static void main(String[] args) throws Exception { if (args.length != 1) { System.out.println("Usage: java examples.jms.queue.QueueSend WebLogicURL"); return; } InitialContext ic = getInitialContext(args[0]); QueueSend qs = new QueueSend(); qs.init(ic, QUEUE); readAndSend(qs); qs.close(); } private static void readAndSend(QueueSend qs) throws IOException, JMSException { BufferedReader msgStream = new BufferedReader(new InputStreamReader(System.in)); String line=null; boolean quitNow = false; do { System.out.print("Enter message (\"quit\" to quit): \n"); line = msgStream.readLine(); if (line != null && line.trim().length() != 0) { qs.send(line); System.out.println("JMS Message Sent: "+line+"\n"); quitNow = line.equalsIgnoreCase("quit"); } } while (! quitNow); } private static InitialContext getInitialContext(String url) throws NamingException { Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY, JNDI_FACTORY); env.put(Context.PROVIDER_URL, url); return new InitialContext(env); } } 2. How to Use This Class 2.1 From the file system on UNIX/Linux Log in to a machine with a WebLogic installation and create a directory to contain the source and code matching the package name, e.g. $HOME/examples/jms/queue. Copy the above QueueSend.java file to this directory. Set the CLASSPATH and environment to match the WebLogic server environment. Go to $MIDDLEWARE_HOME/user_projects/domains/base_domain/bin  and execute . ./setDomainEnv.sh Collect the following information required to run the script: The JNDI name of a JMS queue to use In the Weblogic server console > Services > Messaging > JMS Modules > (Module name, e.g. TestJMSModule) > (JMS queue name, e.g. TestJMSQueue)Select the queue and note its JNDI name, e.g. jms/TestJMSQueue The JNDI name of a connection factory to connect to the queue Follow the same path as above to get the connection factory for the above queue, e.g. TestConnectionFactory and its JNDI namee.g. jms/TestConnectionFactory The URL and port of the WebLogic server running the above queue Check the JMS server for the above queue and the managed server it is targeted to, for example soa_server1. Now find the port this managed server is listening on, by looking at its entry under Environment > Servers in the WLS console, e.g. 8001 The URL for the server to be given to the QueueSend program in this example will therefore be t3://host.domain:8001 e.g. t3://jbevans-lx.de.oracle.com:8001 Edit QueueSend.java and enter the above queue name and connection factory respectively under ...public final static String  JMS_FACTORY=" jms/TestConnectionFactory "; ... public final static String QUEUE=" jms/TestJMSQueue "; ... Compile QueueSend.java using javac QueueSend.java Go to the source’s top-level directory and execute it using java examples.jms.queue.QueueSend t3://jbevans-lx.de.oracle.com:8001 This will prompt for a text input or “quit” to end. In the WLS console, go to the queue and select Monitoring to confirm that a new message was written to the queue. 2.2 From JDeveloper Create a new application in JDeveloper, called, for example JMSTests. When prompted for a project name, enter QueueSend and select Java as the technology Default Package = examples.jms.queue (but you can enter anything here as you will overwrite it in the code later). Leave the other values at their defaults. Press Finish Create a new Java class called QueueSend and use the default values This will create a file called QueueSend.java. Open QueueSend.java, if it is not already open and replace all its contents with the QueueSend java code listed above Some lines might have warnings due to unfound objects. These are due to missing libraries in the JDeveloper project. Add the following libraries to the JDeveloper project: right-click the QueueSend  project in the navigation menu and select Libraries and Classpath , then Add JAR/Directory  Go to the folder containing the JDeveloper installation and find/choose the file javax.jms_1.1.1.jar , e.g. at D:\oracle\jdev11116\modules\javax.jms_1.1.1.jar Do the same for the weblogic.jar file located, for example in D:\oracle\jdev11116\wlserver_10.3\server\lib\weblogic.jar Now you should be able to compile the project, for example by selecting the Make or Rebuild icons   If you try to execute the project, you will get a usage message, as it requires a parameter pointing to the WLS installation containing the JMS queue, for example t3://jbevans-lx.de.oracle.com:8001 . You can automatically pass this parameter to the program from JDeveloper by editing the project’s Run/Debug/Profile. Select the project properties, select Run/Debug/Profile and edit the Default run configuration and add the connection parameter to the Program Arguments field If you execute it again, you will see that it has passed the parameter to the start command If you get a ClassNotFoundException for the class weblogic.jndi.WLInitialContextFactory , then check that the weblogic.jar file was correctly added to the project in one of the earlier steps above. Set the values of JMS_FACTORY and QUEUE the same way as described above in the description of how to use this from a Linux file system, i.e. ...public final static String  JMS_FACTORY=" jms/TestConnectionFactory "; ... public final static String QUEUE=" jms/TestJMSQueue "; ... You need to make one more change to the project. If you execute it now, it will prompt for the payload for the JMS message, but you won’t be able to enter it by default in JDeveloper. You need to enable program input for the project first. Select the project’s properties, then Tool Settings, then check the Allow Program Input checkbox at the bottom and Save. Now when you execute the project, you will get a text entry field at the bottom into which you can enter the payload. You can enter multiple messages until you enter “quit”, which will cause the program to stop. The following screen shot shows the TestJMSQueue’s Monitoring page, after a message was sent to the queue: This concludes the sample. In the following post I will show you how to read the message from the queue again.

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  • Special kind of queue

    - by devoured elysium
    I am looking for something like a Queue that would allow me to put elements at the end of the queue and pop them out in the beggining, like a regular Queue does. The difference would be that I also need to compact the Queue from time to time. This is, let's assume I have the following items on my Queue (each character, including the dot, is an item in the Queue): e d . c . b . a (this Queue has 8 items) Then, I'd need for example to remove the last dot, so to get: e d . c . b a Is there anything like that in the Java Collection classes? I need to use this for a program I am doing where I can't use anything but Java's classes. I am not allowed to design one for myself. Currently I'm just using a LinkedList, but I thought maybe this would be more like a Queue than a LinkedList. Thanks

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  • How to monitor current output/receive queue length in Linux

    - by IZhen
    I want to check the capacity and performance of my network. Besides checking the txkB/s and rxkB/s via Sar, I'd also like to see the average queue length of the network interface(so that the average queueing time in the interface can be calculated). It seems that netstat can give a per socket queue length, is it possible to get a per interface statics(a bit like Network Interface\Output Queue Length in Windows)? A related and kind of reverse questions is How do I view the TCP Send and Receive Queue sizes on Windows? Thanks

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  • SMTP Remote Queue on Exchange 2003

    - by Adam
    We are currently using Windows Server 2003 R2 with Exchange 2003 and SolarWinds Exchange Monitor to monitor. A couple of weeks ago the SMTP remote queue began to build up and it got to about 150 messages in the queue when it began to go down. For the last couple of days the queue has been building up and it has now reached 450 messages. Is there anyway that i can clear this and is it anything that I need to worry about? Thanks guys!

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  • Send documents to printer without waiting for Vista to handle queue

    - by Greenleader
    I got a print server on our old printer. Vista has its own queue which presents a problem. I want to bypass this queue and send everything straight away to the printer so the print server deals with the queue and not Vista. Problem is when a second document is being printed from the same computer after first one. Vista is still waiting for info on finishing the first job even 5 minutes after it was REALLY finished. How do I get it so that I can send straight to the print server and not have Vista slow things down by trying to handle the queue itself?

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  • Java: Implement own message queue (threadsafe)

    - by derMax
    The task is to implement my own messagequeue that is thread safe. My approach: public class MessageQueue { /** * Number of strings (messages) that can be stored in the queue. */ private int capacity; /** * The queue itself, all incoming messages are stored in here. */ private Vector<String> queue = new Vector<String>(capacity); /** * Constructor, initializes the queue. * * @param capacity The number of messages allowed in the queue. */ public MessageQueue(int capacity) { this.capacity = capacity; } /** * Adds a new message to the queue. If the queue is full, it waits until a message is released. * * @param message */ public synchronized void send(String message) { //TODO check } /** * Receives a new message and removes it from the queue. * * @return */ public synchronized String receive() { //TODO check return "0"; } } If the queue is empty and I call remove(), I want to call wait() so that another thread can use the send() method. Respectively, I have to call notifyAll() after every iteration. Question: Is that possible? I mean does it work that when I say wait() in one method of an object, that I can then execute another method of the same object? And another question: Does that seem to be clever?

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  • .net 4.0 concurrent queue dictionary

    - by freddy smith
    I would like to use the new concurrent collections in .NET 4.0 to solve the following problem. The basic data structure I want to have is a producer consumer queue, there will be a single consumer and multiple producers. There are items of type A,B,C,D,E that will be added to this queue. Items of type A,B,C are added to the queue in the normal manner and processed in order. However items of type D or E can only exist in the queue zero or once. If one of these is to be added and there already exists another of the same type that has not yet been processed then this should update that other one in-place in the queue. The queue position would not change (i.e. would not go to the back of the queue) after the update. Which .NET 4.0 classes would be best for this?

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  • Custom Task Queue in App Engine?

    - by demos
    I have created a new task queue and defined it in queue.yaml I am not sure how to start adding tasks to this queue? with the default queue it is simple taskqueue.add(...) how do we do it for a custom queue?

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  • Mac OS X Server (10.5) mail trapped in queue

    - by Meltemi
    We've got mail accumulating in our Leopard Server's queue and not sure exactly why. This machine has required little maintenance over the years so I'm hoping someone here spot the obvious and save us some time. Let me know what other information would be helfull. Server appears to be functioning normally except for "clogged" queue and the following error associated with each "trapped" message: Looking at messages in the queue each one states something like this: Message ID: 4213C3B8B3F Date: October 27, 2009 11:33:27 AM Size: 1824 Sender: [email protected] Recipient(s) & Status: ---------------------- [email protected]: connect to 127.0.0.1[127.0.0.1]: Connection refused Under SettingsRelay we have checked Accept SMTP relays only from these hosts and networks: 127.0.0.0/8 10.0.1.0/24 The mail in queue is addressed to users whose accounts are on this server. Mail.app on the client appears to be functioning normally and checking checking mail on the server. We did add a virtual domain some time ago but all that was working fine for some time... This just started happening recently...any ideas? Edit: toggling the filter services on and off seems to have fixed this except for 2 remaining queued messages that show "mail transport unavailable" as an error!?!

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  • Mail queue directory stuck in IIS SMTP server

    - by Loftx
    Hi there, We have an IIS SMTP server which sends out a largish number of mails (4000 or so) in batches overnight, and recently we've seen mails get "stuck" in the queue directory. Normally restarting the SMTP service seems to fix this, but it's happened a few times so I'm looking for more information. We sent out around 12,000 emails last night in 3 batches of roughly 4000. Around 10 hours later there are still 2000 or so in the queue directory which don't seem to be leaving the queue. Any new mails which appear in the queue are picked up almost immediately and sent to their destination, but these 2000 or so don't seem to move. Looking at the date modified on the emails some match up with the time they were sent, but around 1000 of them have modified dates stretching up to now. e.g. there was one mail with a date in the message headers of 5:30 this morning, but it's date modified is 11:50 and there are 3 other messages with a date modified of 11:50, then 5 with 11:49, 2 with 11:45 stretching back for a few hours and all with actual message headers far earlier. The logs for the server look like this 11:54:52 127.0.0.1 EHLO - 250 11:54:52 127.0.0.1 MAIL - 250 11:54:52 127.0.0.1 RCPT - 250 11:54:52 127.0.0.1 DATA - 250 11:54:52 127.0.0.1 QUIT - 240 11:54:53 85.115.62.190 - - 0 11:54:53 85.115.62.190 EHLO - 0 11:54:53 85.115.62.190 - - 0 11:54:53 85.115.62.190 MAIL - 0 11:54:53 85.115.62.190 - - 0 11:54:53 85.115.62.190 RCPT - 0 11:54:53 85.115.62.190 - - 0 11:54:53 85.115.62.190 DATA - 0 11:54:53 85.115.62.190 - - 0 11:54:54 85.115.62.190 - - 0 11:54:54 85.115.62.190 QUIT - 0 11:54:54 85.115.62.190 - - 0 All codes are either 250 or 240 or 0. I believe 250 and 240 indicate success, but I don't know what all the 0s are. Could someone with more experience of mail server troubleshooting give me a hand or tell me what to try next. Thanks, Tom

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  • JMS Step 1 - How to Create a Simple JMS Queue in Weblogic Server 11g

    - by John-Brown.Evans
    JMS Step 1 - How to Create a Simple JMS Queue in Weblogic Server 11g ol{margin:0;padding:0} .c5{vertical-align:top;width:156pt;border-style:solid;border-color:#000000;border-width:1pt;padding:0pt 2pt 0pt 2pt} .c7{list-style-type:disc;margin:0;padding:0} .c4{background-color:#ffffff} .c14{color:#1155cc;text-decoration:underline} .c6{height:11pt;text-align:center} .c13{color:inherit;text-decoration:inherit} .c3{padding-left:0pt;margin-left:36pt} .c0{border-collapse:collapse} .c12{text-align:center} .c1{direction:ltr} .c8{background-color:#f3f3f3} .c2{line-height:1.0} .c11{font-style:italic} .c10{height:11pt} .c9{font-weight:bold} .title{padding-top:24pt;line-height:1.15;text-align:left;color:#000000;font-size:36pt;font-family:"Arial";font-weight:bold;padding-bottom:6pt}.subtitle{padding-top:18pt;line-height:1.15;text-align:left;color:#666666;font-style:italic;font-size:24pt;font-family:"Georgia";padding-bottom:4pt} li{color:#000000;font-size:10pt;font-family:"Arial"} p{color:#000000;font-size:10pt;margin:0;font-family:"Arial"} h1{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-size:18pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h2{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-size:14pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h3{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-size:12pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h4{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-style:italic;font-size:11pt;font-family:"Arial";padding-bottom:0pt} h5{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-size:10pt;font-family:"Arial";font-weight:normal;padding-bottom:0pt} h6{padding-top:0pt;line-height:1.15;text-align:left;color:#666;font-style:italic;font-size:10pt;font-family:"Arial";padding-bottom:0pt} This example shows the steps to create a simple JMS queue in WebLogic Server 11g for testing purposes. For example, to use with the two sample programs QueueSend.java and QueueReceive.java which will be shown in later examples. Additional, detailed information on JMS can be found in the following Oracle documentation: Oracle® Fusion Middleware Configuring and Managing JMS for Oracle WebLogic Server 11g Release 1 (10.3.6) Part Number E13738-06 http://docs.oracle.com/cd/E23943_01/web.1111/e13738/toc.htm 1. Introduction and Definitions A JMS queue in Weblogic Server is associated with a number of additional resources: JMS Server A JMS server acts as a management container for resources within JMS modules. Some of its responsibilities include the maintenance of persistence and state of messages and subscribers. A JMS server is required in order to create a JMS module. JMS Module A JMS module is a definition which contains JMS resources such as queues and topics. A JMS module is required in order to create a JMS queue. Subdeployment JMS modules are targeted to one or more WLS instances or a cluster. Resources within a JMS module, such as queues and topics are also targeted to a JMS server or WLS server instances. A subdeployment is a grouping of targets. It is also known as advanced targeting. Connection Factory A connection factory is a resource that enables JMS clients to create connections to JMS destinations. JMS Queue A JMS queue (as opposed to a JMS topic) is a point-to-point destination type. A message is written to a specific queue or received from a specific queue. The objects used in this example are: Object Name Type JNDI Name TestJMSServer JMS Server TestJMSModule JMS Module TestSubDeployment Subdeployment TestConnectionFactory Connection Factory jms/TestConnectionFactory TestJMSQueue JMS Queue jms/TestJMSQueue 2. Configuration Steps The following steps are done in the WebLogic Server Console, beginning with the left-hand navigation menu. 2.1 Create a JMS Server Services > Messaging > JMS Servers Select New Name: TestJMSServer Persistent Store: (none) Target: soa_server1  (or choose an available server) Finish The JMS server should now be visible in the list with Health OK. 2.2 Create a JMS Module Services > Messaging > JMS Modules Select New Name: TestJMSModule Leave the other options empty Targets: soa_server1  (or choose the same one as the JMS server)Press Next Leave “Would you like to add resources to this JMS system module” unchecked and  press Finish . 2.3 Create a SubDeployment A subdeployment is not necessary for the JMS queue to work, but it allows you to easily target subcomponents of the JMS module to a single target or group of targets. We will use the subdeployment in this example to target the following connection factory and JMS queue to the JMS server we created earlier. Services > Messaging > JMS Modules Select TestJMSModule Select the Subdeployments  tab and New Subdeployment Name: TestSubdeployment Press Next Here you can select the target(s) for the subdeployment. You can choose either Servers (i.e. WebLogic managed servers, such as the soa_server1) or JMS Servers such as the JMS Server created earlier. As the purpose of our subdeployment in this example is to target a specific JMS server, we will choose the JMS Server option. Select the TestJMSServer created earlier Press Finish 2.4  Create a Connection Factory Services > Messaging > JMS Modules Select TestJMSModule  and press New Select Connection Factory  and Next Name: TestConnectionFactory JNDI Name: jms/TestConnectionFactory Leave the other values at default On the Targets page, select the Advanced Targeting  button and select TestSubdeployment Press Finish The connection factory should be listed on the following page with TestSubdeployment and TestJMSServer as the target. 2.5 Create a JMS Queue Services > Messaging > JMS Modules Select TestJMSModule  and press New Select Queue and Next Name: TestJMSQueueJNDI Name: jms/TestJMSQueueTemplate: NonePress Next Subdeployments: TestSubdeployment Finish The TestJMSQueue should be listed on the following page with TestSubdeployment and TestJMSServer. Confirm the resources for the TestJMSModule. Using the Domain Structure tree, navigate to soa_domain > Services > Messaging > JMS Modules then select TestJMSModule You should see the following resources The JMS queue is now complete and can be accessed using the JNDI names jms/TestConnectionFactory andjms/TestJMSQueue. In the following blog post in this series, I will show you how to write a message to this queue, using the WebLogic sample Java program QueueSend.java.

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  • Clojure agents consuming from a queue

    - by erikcw
    I'm trying to figure out the best way to use agents to consume items from a Message Queue (Amazon SQS). Right now I have a function (process-queue-item) that grabs an items from the queue, and processes it. I want to process these items concurrently, but I can't wrap my head around how to control the agents. Basically I want to keep all of the agents busy as much as possible without pulling to many items from the Queue and developing a backlog (I'll have this running on a couple of machines, so items need to be left in the queue until they are really needed). Can anyone give me some pointers on improving my implementation? (def active-agents (ref 0)) (defn process-queue-item [_] (dosync (alter active-agents inc)) ;retrieve item from Message Queue (Amazon SQS) and process (dosync (alter active-agents dec))) (defn -main [] (def agents (for [x (range 20)] (agent x))) (loop [loop-count 0] (if (< @active-agents 20) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent)) ;should skip this agent until later if it is still busy processing (not sure how) (send-off agent process-queue-item))) ;(apply await-for (* 10 1000) agents) (Thread/sleep 10000) (logging/info (str "ACTIVE AGENTS " @active-agents)) (if (> 10 loop-count) (do (logging/info (str "done, let's cleanup " count)) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent))) (apply await agents) (shutdown-agents)) (recur (inc count)))))

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  • Pointers to structures

    - by blacktooth
    typedef struct queue { int q[max]; int qhead; int qrear; } queue; void init_queue(queue *QUEUE) { QUEUE.qhead = 0; QUEUE.qrear = -1; } void enqueue(queue *QUEUE,int data) { QUEUE.qrear++; QUEUE.q[QUEUE.qrear] = data; } int process_queue(queue *QUEUE) { if(QUEUE.qhead > QUEUE.qrear) return -1; else return QUEUE.q[QUEUE.qhead++]; } I am implementing queues using arrays just to keep it simple. Wats the error with the above code?

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