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  • Migrating SQL Server Databases – The DBA’s Checklist (Part 1)

    - by Sadequl Hussain
    It is a fact of life: SQL Server databases change homes. They move from one instance to another, from one version to the next, from old servers to new ones.  They move around as an organisation’s data grows, applications are enhanced or new versions of the database software are released. If not anything else, servers become old and unreliable and databases eventually need to find a new home. Consider the following scenarios: 1.     A new  database application is rolled out in a production server from the development or test environment 2.     A copy of the production database needs to be installed in a test server for troubleshooting purposes 3.     A copy of the development database is regularly refreshed in a test server during the system development life cycle 4.     A SQL Server is upgraded to a newer version. This can be an in-place upgrade or a side-by-side migration 5.     One or more databases need to be moved between different instances as part of a consolidation strategy. The instances can be running the same or different version of SQL Server 6.     A database has to be restored from a backup file provided by a third party application vendor 7.     A backup of the database is restored in the same or different instance for disaster recovery 8.     A database needs to be migrated within the same instance: a.     Files are moved from direct attached storage to storage area network b.    The same database is copied under a different name for another application Migrating SQL Server database applications is a complex topic in itself. There are a number of components that can be involved: jobs, DTS or SSIS packages, logins or linked servers are only few pieces of the puzzle. However, in this article we will focus only on the central part of migration: the installation of the database itself. Unless it is an in-place upgrade, typically the database is taken from a source server and installed in a destination instance.  Most of the time, a full backup file is used for the rollout. The backup file is either provided to the DBA or the DBA takes the backup and restores it in the target server. Sometimes the database is detached from the source and the files are copied to and attached in the destination. Regardless of the method of copying, moving, refreshing, restoring or upgrading the physical database, there are a number of steps the DBA should follow before and after it has been installed in the destination. It is these post database installation steps we are going to discuss below. Some of these steps apply in almost every scenario described above while some will depend on the type of objects contained within the database.  Also, the principles hold regardless of the number of databases involved. Step 1:  Make a copy of data and log files when attaching and detaching When detaching and attaching databases, ensure you have made copies of the data and log files if the destination is running a newer version of SQL Server. This is because once attached to a newer version, the database cannot be detached and attached back to an older version. Trying to do so will give you a message like the following: Server: Msg 602, Level 21, State 50, Line 1 Could not find row in sysindexes for database ID 6, object ID 1, index ID 1. Run DBCC CHECKTABLE on sysindexes. Connection Broken If you try to backup the attached database and restore it in the source, it will still fail. Similarly, if you are restoring the database in a newer version, it cannot be backed up or detached and put back in an older version of SQL. Unlike detach and attach method though, you do not lose the backup file or the original database here. When detaching and attaching a database, it is important you keep all the log files available along with the data files. It is possible to attach a database without a log file and SQL Server can be instructed to create a new log file, however this does not work if the database was detached when the primary file group was read-only. You will need all the log files in such cases. Step 2: Change database compatibility level Once the database has been restored or attached to a newer version of SQL Server, change the database compatibility level to reflect the newer version unless there is a compelling reason not to do so. When attaching or restoring from a previous version of SQL, the database retains the older version’s compatibility level.  The only time you would want to keep a database with an older compatibility level is when the code within your database is no longer supported by SQL Server. For example, outer joins with *= or the =* operators were still possible in SQL 2000 (with a warning message), but not in SQL 2005 anymore. If your stored procedures or triggers are using this form of join, you would want to keep the database with an older compatibility level.  For a list of compatibility issues between older and newer versions of SQL Server databases, refer to the Books Online under the sp_dbcmptlevel topic. Application developers and architects can help you in deciding whether you should change the compatibility level or not. You can always change the compatibility mode from the newest to an older version if necessary. To change the compatibility level, you can either use the database’s property from the SQL Server Management Studio or use the sp_dbcmptlevel stored procedure.   Bear in mind that you cannot run the built-in reports for databases from SQL Server Management Studio if you keep the database with an older compatibility level. The following figure shows the error message I received when trying to run the “Disk Usage by Top Tables” report against a database. This database was hosted in a SQL Server 2005 system and still had a compatibility mode 80 (SQL 2000).     Continues…

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  • Migrating SQL Server Databases – The DBA’s Checklist (Part 3)

    - by Sadequl Hussain
    Continuing from Part 2 of the Database Migration Checklist series: Step 10: Full-text catalogs and full-text indexing This is one area of SQL Server where people do not seem to take notice unless something goes wrong. Full-text functionality is a specialised area in database application development and is not usually implemented in your everyday OLTP systems. Nevertheless, if you are migrating a database that uses full-text indexing on one or more tables, you need to be aware a few points. First of all, SQL Server 2005 now allows full-text catalog files to be restored or attached along with the rest of the database. However, after migration, if you are unable to look at the properties of any full-text catalogs, you are probably better off dropping and recreating it. You may also get the following error messages along the way: Msg 9954, Level 16, State 2, Line 1 The Full-Text Service (msftesql) is disabled. The system administrator must enable this service. This basically means full text service is not running (disabled or stopped) in the destination instance. You will need to start it from the Configuration Manager. Similarly, if you get the following message, you will also need to drop and recreate the catalog and populate it. Msg 7624, Level 16, State 1, Line 1 Full-text catalog ‘catalog_name‘ is in an unusable state. Drop and re-create this full-text catalog. A full population of full-text indexes can be a time and resource intensive operation. Obviously you will want to schedule it for low usage hours if the database is restored in an existing production server. Also, bear in mind that any scheduled job that existed in the source server for populating the full text catalog (e.g. nightly process for incremental update) will need to be re-created in the destination. Step 11: Database collation considerations Another sticky area to consider during a migration is the collation setting. Ideally you would want to restore or attach the database in a SQL Server instance with the same collation. Although not used commonly, SQL Server allows you to change a database’s collation by using the ALTER DATABASE command: ALTER DATABASE database_name COLLATE collation_name You should not be using this command for no reason as it can get really dangerous.  When you change the database collation, it does not change the collation of the existing user table columns.  However the columns of every new table, every new UDT and subsequently created variables or parameters in code will use the new setting. The collation of every char, nchar, varchar, nvarchar, text or ntext field of the system tables will also be changed. Stored procedure and function parameters will be changed to the new collation and finally, every character-based system data type and user defined data types will also be affected. And the change may not be successful either if there are dependent objects involved. You may get one or multiple messages like the following: Cannot ALTER ‘object_name‘ because it is being referenced by object ‘dependent_object_name‘. That is why it is important to test and check for collation related issues. Collation also affects queries that use comparisons of character-based data.  If errors arise due to two sides of a comparison being in different collation orders, the COLLATE keyword can be used to cast one side to the same collation as the other. Continues…

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  • Migrating SQL Server Databases – The DBA’s Checklist (Part 2)

    - by Sadequl Hussain
    Continuing from Part 1  , our Migration Checklist continues: Step 5: Update statistics It is always a good idea to update the statistics of the database that you have just installed or migrated. To do this, run the following command against the target database: sp_updatestats The sp_updatestats system stored procedure runs the UPDATE STATISTICS command against every user and system table in the database.  However, a word of caution: running the sp_updatestats against a database with a compatibility level below 90 (SQL Server 2005) will reset the automatic UPDATE STATISTICS settings for every index and statistics of every table in the database. You may therefore want to change the compatibility mode before you run the command. Another thing you should remember to do is to ensure the new database has its AUTO_CREATE_STATISTICS and AUTO_UPDATE_STATISTICS properties set to ON. You can do so using the ALTER DATABASE command or from the SSMS. Step 6: Set database options You may have to change the state of a database after it has been restored. If the database was changed to single-user or read-only mode before backup, the restored copy will also retain these settings. This may not be an issue when you are manually restoring from Enterprise Manager or the Management Studio since you can change the properties. However, this is something to be mindful of if the restore process is invoked by an automated job or script and the database needs to be written to immediately after restore. You may want to check the database’s status programmatically in such cases. Another important option you may want to set for the newly restored / attached database is PAGE_VERIFY. This option specifies how you want SQL Server to ensure the physical integrity of the data. It is a new option from SQL Server 2005 and can have three values: CHECKSUM (default for SQL Server 2005 and latter databases), TORN_PAGE_DETECTION (default when restoring a pre-SQL Server 2005 database) or NONE. Torn page detection was itself an option for SQL Server 2000 databases. From SQL Server 2005, when PAGE_VERIFY is set to CHECKSUM, the database engine calculates the checksum for a page’s contents and writes it to the page header before storing it in disk. When the page is read from the disk, the checksum is computed again and compared with the checksum stored in the header.  Torn page detection works much like the same way in that it stores a bit in the page header for every 512 byte sector. When data is read from the page, the torn page bits stored in the header is compared with the respective sector contents. When PAGE_VERIFY is set to NONE, SQL Server does not perform any checking, even if torn page data or checksums are present in the page header.  This may not be something you would want to set unless there is a very specific reason.  Microsoft suggests using the CHECKSUM page verify option as this offers more protection. Step 7: Map database users to logins A common database migration issue is related to user access. Windows and SQL Server native logins that existed in the source instance and had access to the database may not be present in the destination. Even if the logins exist in the destination, the mapping between the user accounts and the logins will not be automatic. You can use a special system stored procedure called sp_change_users_login to address these situations. The procedure needs to be run against the newly attached or restored database and can accept four parameters. Depending on what you want to do, you may be using less than four though. The first parameter, @Action, can take three values. When you specify @Action = ‘Report’, the system will provide you with a list of database users which are not mapped to any login. If you want to map a database user to an existing SQL Server login, the value for @Action will be ‘Update_One’. In this case, you will only need to provide the database user name and the login it will map to. So if your newly restored database has a user account called “bob” and there is already a SQL Server login with the same name and you want to map the user to the login, you will execute a query like the following: sp_change_users_login         @Action = ‘Update_One’,         @UserNamePattern = ‘bob’,         @LoginName = ‘bob’ If the login does not exist, you can instruct SQL Server to create the login with the same name. In this case you will need to provide a password for the login and the value of the @Action parameter will be ‘Auto_Fix’. If the login already exists, it will be automatically mapped to the user account. Unfortunately sp_change_users_login system stored procedure cannot be used to map database users to trusted logins (Windows accounts) in SQL Server. You will need to follow a manual process to re-map the database user accounts.  Continues…

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  • Importing data from text file to specific columns using BULK INSERT

    - by Dinesh Asanka
    Bulk insert is much faster than using other techniques such as  SSIS. However, when you are using bulk insert you can’t insert to specific columns. If, for example, there are five columns in a table you should have five values for each record in the text file you are importing from. This is an issue when you are expecting default values to be inserted into tables. Let us say you have table as below: In this table, you are expecting ID, Status and CreatedDate to be updated automatically, so your text file may only have   FirstName  LastName  values as below: Dinesh,Asanka Saman,Liyanage Ruwan,Silva Susantha,Bathige Jude,Peires Sanjeewa,Jayawickrama If you use bulk insert to this table like follows, You will be returned an error: Bulk load data conversion error (type mismatch or invalid character for the specified codepage) for row 1, column 1 (ID). To avoid this you will need to create a view with the columns you are expecting to fill and use bulk insert against it. If you check the table now, you will see table with values in the text file and the default values.

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  • Copy Only Backups for Adhoc Backups

    Introduction In most organizations backup plans are implemented using full differential and transactional log backups. The normal scenario would be take a full backup on Sunday (off peak hours), differential backup daily at mid-night and transactional log backups on hourly basis. What ... [Read Full Article]

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  • New T-SQL Features in SQL Server 2011

    - by Divya Agrawal
    SQL Server 2011 (or Denali) CTP is now available and can be downloaded at http://www.microsoft.com/downloads/en/details.aspx?FamilyID=6a04f16f-f6be-4f92-9c92-f7e5677d91f9&displaylang=en SQL Server 2011 has several major enhancements including a new look for SSMS. SSMS is now   similar to Visual Studio   with greatly improved Intellisense support. This article we will focus on the T-SQL Enhancements in SQL Server 2011. The main [...]

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  • Implementing Database Settings Using Policy Based Management

    - by Ashish Kumar Mehta
    Introduction Database Administrators have always had a tough time to ensuring that all the SQL Servers administered by them are configured according to the policies and standards of organization. Using SQL Server’s  Policy Based Management feature DBAs can now manage one or more instances of SQL Server 2008 and check for policy compliance issues. In this article we will utilize Policy Based Management (aka Declarative Management Framework or DMF) feature of SQL Server to implement and verify database settings on all production databases. It is best practice to enforce the below settings on each Production database. However, it can be tedious to go through each database and then check whether the below database settings are implemented across databases. In this article I will explain it to you how to utilize the Policy Based Management Feature of SQL Server 2008 to create a policy to verify these settings on all databases and in cases of non-complaince how to bring them back into complaince. Database setting to enforce on each user database : Auto Close and Auto Shrink Properties of database set to False Auto Create Statistics and Auto Update Statistics set to True Compatibility Level of all the user database set as 100 Page Verify set as CHECKSUM Recovery Model of all user database set to Full Restrict Access set as MULTI_USER Configure a Policy to Verify Database Settings 1. Connect to SQL Server 2008 Instance using SQL Server Management Studio 2. In the Object Explorer, Click on Management > Policy Management and you will be able to see Policies, Conditions & Facets as child nodes 3. Right click Policies and then select New Policy…. from the drop down list as shown in the snippet below to open the  Create New Policy Popup window. 4. In the Create New Policy popup window you need to provide the name of the policy as “Implementing and Verify Database Settings for Production Databases” and then click the drop down list under Check Condition. As highlighted in the snippet below click on the New Condition… option to open up the Create New Condition window. 5. In the Create New Condition popup window you need to provide the name of the condition as “Verify and Change Database Settings”. In the Facet drop down list you need to choose the Facet as Database Options as shown in the snippet below. Under Expression you need to select Field value as @AutoClose and then choose Operator value as ‘ = ‘ and finally choose Value as False. Now that you have successfully added the first field you can now go ahead and add rest of the fields as shown in the snippet below. Once you have successfully added all the above shown fields of Database Options Facet, click OK to save the changes and to return to the parent Create New Policy – Implementing and Verify Database Settings for Production Database windows where you will see that the newly created condition “Verify and Change Database Settings” is selected by default. Continues…

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  • Whether to use UNION or OR in SQL Server Queries

    - by Dinesh Asanka
    Recently I came across with an article on DB2 about using Union instead of OR. So I thought of carrying out a research on SQL Server on what scenarios UNION is optimal in and which scenarios OR would be best. I will analyze this with a few scenarios using samples taken  from the AdventureWorks database Sales.SalesOrderDetail table. Scenario 1: Selecting all columns So we are going to select all columns and you have a non-clustered index on the ProductID column. --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR ProductID =709 OR ProductID =998 OR ProductID =875 OR ProductID =976 OR ProductID =874 --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 709 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 998 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 875 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 976 UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 874 So query 1 is using OR and the later is using UNION. Let us analyze the execution plans for these queries. Query 1 Query 2 As expected Query 1 will use Clustered Index Scan but Query 2, uses all sorts of things. In this case, since it is using multiple CPUs you might have CX_PACKET waits as well. Let’s look at the profiler results for these two queries: CPU Reads Duration Row Counts OR 78 1252 389 3854 UNION 250 7495 660 3854 You can see from the above table the UNION query is not performing well as the  OR query though both are retuning same no of rows (3854).These results indicate that, for the above scenario UNION should be used. Scenario 2: Non-Clustered and Clustered Index Columns only --Query 1 : OR SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR ProductID =709 OR ProductID =998 OR ProductID =875 OR ProductID =976 OR ProductID =874 GO --Query 2 : UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 709 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 998 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 875 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 976 UNION SELECT ProductID,SalesOrderID, SalesOrderDetailID FROM Sales.SalesOrderDetail WHERE ProductID = 874 GO So this time, we will be selecting only index columns, which means these queries will avoid a data page lookup. As in the previous case we will analyze the execution plans: Query 1 Query 2 Again, Query 2 is more complex than Query 1. Let us look at the profile analysis: CPU Reads Duration Row Counts OR 0 24 208 3854 UNION 0 38 193 3854 In this analyzis, there is only slight difference between OR and UNION. Scenario 3: Selecting all columns for different fields Up to now, we were using only one column (ProductID) in the where clause.  What if we have two columns for where clauses and let us assume both are covered by non-clustered indexes? --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR CarrierTrackingNumber LIKE 'D0B8%' --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE CarrierTrackingNumber  LIKE 'D0B8%' Query 1 Query 2: As we can see, the query plan for the second query has improved. Let us see the profiler results. CPU Reads Duration Row Counts OR 47 1278 443 1228 UNION 31 1334 400 1228 So in this case too, there is little difference between OR and UNION. Scenario 4: Selecting Clustered index columns for different fields Now let us go only with clustered indexes: --Query 1 : OR SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 OR CarrierTrackingNumber LIKE 'D0B8%' --Query 2 : UNION SELECT * FROM Sales.SalesOrderDetail WHERE ProductID = 714 UNION SELECT * FROM Sales.SalesOrderDetail WHERE CarrierTrackingNumber  LIKE 'D0B8%' Query 1 Query 2 Now both execution plans are almost identical except is an additional Stream Aggregate is used in the first query. This means UNION has advantage over OR in this scenario. Let us see profiler results for these queries again. CPU Reads Duration Row Counts OR 0 319 366 1228 UNION 0 50 193 1228 Now see the differences, in this scenario UNION has somewhat of an advantage over OR. Conclusion Using UNION or OR depends on the scenario you are faced with. So you need to do your analyzing before selecting the appropriate method. Also, above the four scenarios are not all an exhaustive list of scenarios, I selected those for the broad description purposes only.

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  • In MySQL, what is the most effective query design for joining large tables with many to many relatio

    - by lighthouse65
    In our application, we collect data on automotive engine performance -- basically source data on engine performance based on the engine type, the vehicle running it and the engine design. Currently, the basis for new row inserts is an engine on-off period; we monitor performance variables based on a change in engine state from active to inactive and vice versa. The related engineState table looks like this: +---------+-----------+---------------+---------------------+---------------------+-----------------+ | vehicle | engine | engine_state | state_start_time | state_end_time | engine_variable | +---------+-----------+---------------+---------------------+---------------------+-----------------+ | 080025 | E01 | active | 2008-01-24 16:19:15 | 2008-01-24 16:24:45 | 720 | | 080028 | E02 | inactive | 2008-01-24 16:19:25 | 2008-01-24 16:22:17 | 304 | +---------+-----------+---------------+---------------------+---------------------+-----------------+ For a specific analysis, we would like to analyze table content based on a row granularity of minutes, rather than the current basis of active / inactive engine state. For this, we are thinking of creating a simple productionMinute table with a row for each minute in the period we are analyzing and joining the productionMinute and engineEvent tables on the date-time columns in each table. So if our period of analysis is from 2009-12-01 to 2010-02-28, we would create a new table with 129,600 rows, one for each minute of each day for that three-month period. The first few rows of the productionMinute table: +---------------------+ | production_minute | +---------------------+ | 2009-12-01 00:00 | | 2009-12-01 00:01 | | 2009-12-01 00:02 | | 2009-12-01 00:03 | +---------------------+ The join between the tables would be engineState AS es LEFT JOIN productionMinute AS pm ON es.state_start_time <= pm.production_minute AND pm.production_minute <= es.event_end_time. This join, however, brings up multiple environmental issues: The engineState table has 5 million rows and the productionMinute table has 130,000 rows When an engineState row spans more than one minute (i.e. the difference between es.state_start_time and es.state_end_time is greater than one minute), as is the case in the example above, there are multiple productionMinute table rows that join to a single engineState table row When there is more than one engine in operation during any given minute, also as per the example above, multiple engineState table rows join to a single productionMinute row In testing our logic and using only a small table extract (one day rather than 3 months, for the productionMinute table) the query takes over an hour to generate. In researching this item in order to improve performance so that it would be feasible to query three months of data, our thoughts were to create a temporary table from the engineEvent one, eliminating any table data that is not critical for the analysis, and joining the temporary table to the productionMinute table. We are also planning on experimenting with different joins -- specifically an inner join -- to see if that would improve performance. What is the best query design for joining tables with the many:many relationship between the join predicates as outlined above? What is the best join type (left / right, inner)?

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  • Monitor SQL Server Replication Jobs

    - by Yaniv Etrogi
    The Replication infrastructure in SQL Server is implemented using SQL Server Agent to execute the various components involved in the form of a job (e.g. LogReader agent job, Distribution agent job, Merge agent job) SQL Server jobs execute a binary executable file which is basically C++ code. You can download all the scripts for this article here SQL Server Job Schedules By default each of job has only one schedule that is set to Start automatically when SQL Server Agent starts. This schedule ensures that when ever the SQL Server Agent service is started all the replication components are also put into action. This is OK and makes sense but there is one problem with this default configuration that needs improvement  -  if for any reason one of the components fails it remains down in a stopped state.   Unless you monitor the status of each component you will typically get to know about such a failure from a customer complaint as a result of missing data or data that is not up to date at the subscriber level. Furthermore, having any of these components in a stopped state can lead to more severe problems if not corrected within a short time. The action required to improve on this default settings is in fact very simple. Adding a second schedule that is set as a Daily Reoccurring schedule which runs every 1 minute does the trick. SQL Server Agent’s scheduler module knows how to handle overlapping schedules so if the job is already being executed by another schedule it will not get executed again at the same time. So, in the event of a failure the failed job remains down for at most 60 seconds. Many DBAs are not aware of this capability and so search for more complex solutions such as having an additional dedicated job running an external code in VBS or another scripting language that detects replication jobs in a stopped state and starts them but there is no need to seek such external solutions when what is needed can be accomplished by T-SQL code. SQL Server Jobs Status In addition to the 1 minute schedule we also want to ensure that key components in the replication are enabled so I can search for those components by their Category, and set their status to enabled in case they are disabled, by executing the stored procedure MonitorEnableReplicationAgents. The jobs that I typically have handled are listed below but you may want to extend this, so below is the query to return all jobs along with their category. SELECT category_id, name FROM msdb.dbo.syscategories ORDER BY category_id; Distribution Cleanup LogReader Agent Distribution Agent Snapshot Agent Jobs By default when a publication is created, a snapshot agent job also gets created with a daily schedule. I see more organizations where the snapshot agent job does not need to be executed automatically by the SQL Server Agent  scheduler than organizations who   need a new snapshot generated automatically. To assure this setting is in place I created the stored procedure MonitorSnapshotAgentsSchedules which disables snapshot agent jobs and also deletes the job schedule. It is worth mentioning that when the publication property immediate_sync is turned off then the snapshot files are not created when the Snapshot agent is executed by the job. You control this property when the publication is created with a parameter called @immediate_sync passed to sp_addpublication and for an existing publication you can use sp_changepublication. Implementation The scripts assume the existence of a database named PerfDB. Steps: Run the scripts to create the stored procedures in the PerfDB database. Create a job that executes the stored procedures every hour. -- Verify that the 1_Minute schedule exists. EXEC PerfDB.dbo.MonitorReplicationAgentsSchedules @CategoryId = 10; /* Distribution */ EXEC PerfDB.dbo.MonitorReplicationAgentsSchedules @CategoryId = 13; /* LogReader */ -- Verify all replication agents are enabled. EXEC PerfDB.dbo.MonitorEnableReplicationAgents @CategoryId = 10; /* Distribution */ EXEC PerfDB.dbo.MonitorEnableReplicationAgents @CategoryId = 13; /* LogReader */ EXEC PerfDB.dbo.MonitorEnableReplicationAgents @CategoryId = 11; /* Distribution clean up */ -- Verify that Snapshot agents are disabled and have no schedule EXEC PerfDB.dbo.MonitorSnapshotAgentsSchedules; Want to read more of about replication? Check at my replication posts at my blog.

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  • Manage and Monitor Identity Ranges in SQL Server Transactional Replication

    - by Yaniv Etrogi
    Problem When using transactional replication to replicate data in a one way topology from a publisher to a read-only subscriber(s) there is no need to manage identity ranges. However, when using  transactional replication to replicate data in a two way replication topology - between two or more servers there is a need to manage identity ranges in order to prevent a situation where an INSERT commands fails on a PRIMARY KEY violation error  due to the replicated row being inserted having a value for the identity column which already exists at the destination database. Solution There are two ways to address this situation: Assign a range of identity values per each server. Work with parallel identity values. The first method requires some maintenance while the second method does not and so the scripts provided with this article are very useful for anyone using the first method. I will explore this in more detail later in the article. In the first solution set server1 to work in the range of 1 to 1,000,000,000 and server2 to work in the range of 1,000,000,001 to 2,000,000,000.  The ranges are set and defined using the DBCC CHECKIDENT command and when the ranges in this example are well maintained you meet the goal of preventing the INSERT commands to fall due to a PRIMARY KEY violation. The first insert at server1 will get the identity value of 1, the second insert will get the value of 2 and so on while on server2 the first insert will get the identity value of 1000000001, the second insert 1000000002 and so on thus avoiding a conflict. Be aware that when a row is inserted the identity value (seed) is generated as part of the insert command at each server and the inserted row is replicated. The replicated row includes the identity column’s value so the data remains consistent across all servers but you will be able to tell on what server the original insert took place due the range that  the identity value belongs to. In the second solution you do not manage ranges but enforce a situation in which identity values can never get overlapped by setting the first identity value (seed) and the increment property one time only during the CREATE TABLE command of each table. So a table on server1 looks like this: CREATE TABLE T1 (  c1 int NOT NULL IDENTITY(1, 5) PRIMARY KEY CLUSTERED ,c2 int NOT NULL ); And a table on server2 looks like this: CREATE TABLE T1(  c1 int NOT NULL IDENTITY(2, 5) PRIMARY KEY CLUSTERED ,c2 int NOT NULL ); When these two tables are inserted the results of the identity values look like this: Server1:  1, 6, 11, 16, 21, 26… Server2:  2, 7, 12, 17, 22, 27… This assures no identity values conflicts while leaving a room for 3 additional servers to participate in this same environment. You can go up to 9 servers using this method by setting an increment value of 9 instead of 5 as I used in this example. Continues…

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  • Altering a Column Which has a Default Constraint

    - by Dinesh Asanka
    Setting up a default column is a common task for  developers.  But, are we naming those default constraints explicitly? In the below  table creation, for the column, sys_DateTime the default value Getdate() will be allocated. CREATE TABLE SampleTable (ID int identity(1,1), Sys_DateTime Datetime DEFAULT getdate() ) We can check the relevant information from the system catalogs from following query. SELECT sc.name TableName, dc.name DefaultName, dc.definition, OBJECT_NAME(dc.parent_object_id) TableName, dc.is_system_named  FROM sys.default_constraints dc INNER JOIN sys.columns sc ON dc.parent_object_id = sc.object_id AND dc.parent_column_id = sc.column_id and results would be: Most of the above columns are self-explanatory. The last column, is_system_named, is to identify whether the default name was given by the system. As you know, in the above case, since we didn’t provide  any default name, the  system will generate a default name for you. But the problem with these names is that they can differ from environment to environment.  If example if I create this table in different table the default name could be DF__SampleTab__Sys_D__7E6CC920 Now let us create another default and explicitly name it: CREATE TABLE SampleTable2 (ID int identity(1,1), Sys_DateTime Datetime )   ALTER TABLE SampleTable2 ADD CONSTRAINT DF_sys_DateTime_Getdate DEFAULT( Getdate()) FOR Sys_DateTime If we run the previous query again we will be returned the below output. And you can see that last created default name has 0 for is_system_named. Now let us say I want to change the data type of the sys_DateTime column to something else: ALTER TABLE SampleTable2 ALTER COLUMN Sys_DateTime Date This will generate the below error: Msg 5074, Level 16, State 1, Line 1 The object ‘DF_sys_DateTime_Getdate’ is dependent on column ‘Sys_DateTime’. Msg 4922, Level 16, State 9, Line 1 ALTER TABLE ALTER COLUMN Sys_DateTime failed because one or more objects access this column. This means, you need to drop the default constraint before altering it: ALTER TABLE [dbo].[SampleTable2] DROP CONSTRAINT [DF_sys_DateTime_Getdate] ALTER TABLE SampleTable2 ALTER COLUMN Sys_DateTime Date   ALTER TABLE [dbo].[SampleTable2] ADD CONSTRAINT [DF_sys_DateTime_Getdate] DEFAULT (getdate()) FOR [Sys_DateTime] If you have a system named default constraint that can differ from environment to environment and so you cannot drop it as before, you can use the below code template: DECLARE @defaultname VARCHAR(255) DECLARE @executesql VARCHAR(1000)   SELECT @defaultname = dc.name FROM sys.default_constraints dc INNER JOIN sys.columns sc ON dc.parent_object_id = sc.object_id AND dc.parent_column_id = sc.column_id WHERE OBJECT_NAME (parent_object_id) = 'SampleTable' AND sc.name ='Sys_DateTime' SET @executesql = 'ALTER TABLE SampleTable DROP CONSTRAINT ' + @defaultname EXEC( @executesql) ALTER TABLE SampleTable ALTER COLUMN Sys_DateTime Date ALTER TABLE [dbo].[SampleTable] ADD DEFAULT (Getdate()) FOR [Sys_DateTime]

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  • Upgrade SSIS 2005 Packages to SSIS 2008

    There are several enhancements in SSIS 2008 such as enhanced lookup transformation, the development environment for Script Task and Script Component changing from VSA to VSTA, etc. If you intend to upgrade your SSIS 2005 packages to SSIS 2008 ... [Read Full Article]

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