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  • can't send with postfix but I can whith one user

    - by CvR_XX
    I have a postfix and dovecot server but when i try to send an email i get an time -out. Im trying to send with the email [email protected]. A telnet session isn't helping much ether. I get a blank screen. Local it's working fine. My smtp service is running on treadity.com:25. The strange thing is that the logs are completely empty with any info regarding sending emails. Receiving is working alright. Another strange thing is that i've send some message's and that it worked. But that is only with one email. I can still send from that account but other emails are failing any idea's? config file: # See /usr/share/postfix/main.cf.dist for a commented, more complete version # Debian specific: Specifying a file name will cause the first # line of that file to be used as the name. The Debian default # is /etc/mailname. #myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) biff = no # appending .domain is the MUA's job. append_dot_mydomain = no # Uncomment the next line to generate "delayed mail" warnings #delay_warning_time = 4h readme_directory = no # TLS parameters #smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem #smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key #smtpd_use_tls=yes #smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache #smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtpd_tls_cert_file=/etc/ssl/certs/dovecot.pem smtpd_tls_key_file=/etc/ssl/private/dovecot.pem smtpd_use_tls=yes # See /usr/share/postfix/main.cf.dist for a commented, more complete version # Debian specific: Specifying a file name will cause the first # line of that file to be used as the name. The Debian default # is /etc/mailname. #myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) biff = no # appending .domain is the MUA's job. append_dot_mydomain = no # Uncomment the next line to generate "delayed mail" warnings #delay_warning_time = 4h readme_directory = no # TLS parameters #smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem #smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key #smtpd_use_tls=yes #smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache #smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtpd_tls_cert_file=/etc/ssl/certs/dovecot.pem smtpd_tls_key_file=/etc/ssl/private/dovecot.pem smtpd_use_tls=yes # See /usr/share/postfix/main.cf.dist for a commented, more complete version # Debian specific: Specifying a file name will cause the first # line of that file to be used as the name. The Debian default # is /etc/mailname. #myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) biff = no # appending .domain is the MUA's job. append_dot_mydomain = no # Uncomment the next line to generate "delayed mail" warnings #delay_warning_time = 4h readme_directory = no # TLS parameters #smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem #smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key #smtpd_use_tls=yes #smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache #smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtpd_tls_cert_file=/etc/ssl/certs/dovecot.pem smtpd_tls_key_file=/etc/ssl/private/dovecot.pem smtpd_use_tls=yes smtpd_tls_auth_only = yes #Enabling SMTP for authenticated users, and handing off authentication to Dovecot smtpd_sasl_type = dovecot smtpd_sasl_path = private/auth smtpd_sasl_auth_enable = yes 1,1 Top

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  • Now Live: New Java Enterprise Edition 6 Certification Exams

    - by Paul Sorensen
    The new Java Enterprise Edition 6 (EE6) exams are being released into production, effective today (February 21, 2011). If you participated in the beta exams, we appreciate your patience in awaiting your beta scores (there were some initial technical difficulties with these exams that delayed beta review and scoring). While most of the production exams are currently available and most of the beta scores have been mailed, they are not 100% completed. We expect all production exams to be available and all scores to be mailed tentatively by March 31, 2010. We appreciate your patience in receiving your beta scores as we work through some issues that have delayed the release of beta scores for two of these exams. Beta candidates can expect to receive their printed score reports in the mail from Prometric. Please allow 5 business days from the 'date mailed' below to receive your score report. If you have not received it within 5 business days, please contact Prometric. EXAM  PRODUCTIONDATE BETA SCOREMAILED Loading...CX-311-093 Java Platform, Enterprise Edition 6 Enterprise JavaBeans Developer Certified Expert ExamJanuary 12, 2011February 4, 2011CX-311-094 Java Platform, Enterprise Edition 6 Java Persistence API Developer Certified Expert ExamFebruary 1, 2011February 11, 2011CX-311-232 Java Platform, Enterprise Edition 6 Web Services Developer Certified Expert ExamFebruary 8, 2011by March 31, 2011tentative*CX-311-085 Java Platform, Enterprise Edition 6 JavaServer Pages and Servlet Developer Certified Expert Examby March 31, 2011tentative*by March 31, 2011tentative* *Dates are subject to change without notice.Register now at prometric.com/oracle.QUICK LINKSHelp with beta exam score reportOracle Certified Professional, Java Platform, Enterprise Edition 6 JavaServer Pages and Servlet DeveloperOracle Certified Professional, Java Platform, Enterprise Edition 6 Enterprise JavaBeans DeveloperOracle Certified Professional, Java Platform, Enterprise Edition 6 Java Persistence API DeveloperOracle Certified Professional, Java Platform, Enterprise Edition 6 Web Services Developer

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  • 10 Windows Tweaking Myths Debunked

    - by Chris Hoffman
    Windows is big, complicated, and misunderstood. You’ll still stumble across bad advice from time to time when browsing the web. These Windows tweaking, performance, and system maintenance tips are mostly just useless, but some are actively harmful. Luckily, most of these myths have been stomped out on mainstream sites and forums. However, if you start searching the web, you’ll still find websites that recommend you do these things. Erase Cache Files Regularly to Speed Things Up You can free up disk space by running an application like CCleaner, another temporary-file-cleaning utility, or even the Windows Disk Cleanup tool. In some cases, you may even see an old computer speed up when you erase a large amount of useless files. However, running CCleaner or similar utilities every day to erase your browser’s cache won’t actually speed things up. It will slow down your web browsing as your web browser is forced to redownload the files all over again, and reconstruct the cache you regularly delete. If you’ve installed CCleaner or a similar program and run it every day with the default settings, you’re actually slowing down your web browsing. Consider at least preventing the program from wiping out your web browser cache. Enable ReadyBoost to Speed Up Modern PCs Windows still prompts you to enable ReadyBoost when you insert a USB stick or memory card. On modern computers, this is completely pointless — ReadyBoost won’t actually speed up your computer if you have at least 1 GB of RAM. If you have a very old computer with a tiny amount of RAM — think 512 MB — ReadyBoost may help a bit. Otherwise, don’t bother. Open the Disk Defragmenter and Manually Defragment On Windows 98, users had to manually open the defragmentation tool and run it, ensuring no other applications were using the hard drive while it did its work. Modern versions of Windows are capable of defragmenting your file system while other programs are using it, and they automatically defragment your disks for you. If you’re still opening the Disk Defragmenter every week and clicking the Defragment button, you don’t need to do this — Windows is doing it for you unless you’ve told it not to run on a schedule. Modern computers with solid-state drives don’t have to be defragmented at all. Disable Your Pagefile to Increase Performance When Windows runs out of empty space in RAM, it swaps out data from memory to a pagefile on your hard disk. If a computer doesn’t have much memory and it’s running slow, it’s probably moving data to the pagefile or reading data from it. Some Windows geeks seem to think that the pagefile is bad for system performance and disable it completely. The argument seems to be that Windows can’t be trusted to manage a pagefile and won’t use it intelligently, so the pagefile needs to be removed. As long as you have enough RAM, it’s true that you can get by without a pagefile. However, if you do have enough RAM, Windows will only use the pagefile rarely anyway. Tests have found that disabling the pagefile offers no performance benefit. Enable CPU Cores in MSConfig Some websites claim that Windows may not be using all of your CPU cores or that you can speed up your boot time by increasing the amount of cores used during boot. They direct you to the MSConfig application, where you can indeed select an option that appears to increase the amount of cores used. In reality, Windows always uses the maximum amount of processor cores your CPU has. (Technically, only one core is used at the beginning of the boot process, but the additional cores are quickly activated.) Leave this option unchecked. It’s just a debugging option that allows you to set a maximum number of cores, so it would be useful if you wanted to force Windows to only use a single core on a multi-core system — but all it can do is restrict the amount of cores used. Clean Your Prefetch To Increase Startup Speed Windows watches the programs you run and creates .pf files in its Prefetch folder for them. The Prefetch feature works as a sort of cache — when you open an application, Windows checks the Prefetch folder, looks at the application’s .pf file (if it exists), and uses that as a guide to start preloading data that the application will use. This helps your applications start faster. Some Windows geeks have misunderstood this feature. They believe that Windows loads these files at boot, so your boot time will slow down due to Windows preloading the data specified in the .pf files. They also argue you’ll build up useless files as you uninstall programs and .pf files will be left over. In reality, Windows only loads the data in these .pf files when you launch the associated application and only stores .pf files for the 128 most recently launched programs. If you were to regularly clean out the Prefetch folder, not only would programs take longer to open because they won’t be preloaded, Windows will have to waste time recreating all the .pf files. You could also modify the PrefetchParameters setting to disable Prefetch, but there’s no reason to do that. Let Windows manage Prefetch on its own. Disable QoS To Increase Network Bandwidth Quality of Service (QoS) is a feature that allows your computer to prioritize its traffic. For example, a time-critical application like Skype could choose to use QoS and prioritize its traffic over a file-downloading program so your voice conversation would work smoothly, even while you were downloading files. Some people incorrectly believe that QoS always reserves a certain amount of bandwidth and this bandwidth is unused until you disable it. This is untrue. In reality, 100% of bandwidth is normally available to all applications unless a program chooses to use QoS. Even if a program does choose to use QoS, the reserved space will be available to other programs unless the program is actively using it. No bandwidth is ever set aside and left empty. Set DisablePagingExecutive to Make Windows Faster The DisablePagingExecutive registry setting is set to 0 by default, which allows drivers and system code to be paged to the disk. When set to 1, drivers and system code will be forced to stay resident in memory. Once again, some people believe that Windows isn’t smart enough to manage the pagefile on its own and believe that changing this option will force Windows to keep important files in memory rather than stupidly paging them out. If you have more than enough memory, changing this won’t really do anything. If you have little memory, changing this setting may force Windows to push programs you’re using to the page file rather than push unused system files there — this would slow things down. This is an option that may be helpful for debugging in some situations, not a setting to change for more performance. Process Idle Tasks to Free Memory Windows does things, such as creating scheduled system restore points, when you step away from your computer. It waits until your computer is “idle” so it won’t slow your computer and waste your time while you’re using it. Running the “Rundll32.exe advapi32.dll,ProcessIdleTasks” command forces Windows to perform all of these tasks while you’re using the computer. This is completely pointless and won’t help free memory or anything like that — all you’re doing is forcing Windows to slow your computer down while you’re using it. This command only exists so benchmarking programs can force idle tasks to run before performing benchmarks, ensuring idle tasks don’t start running and interfere with the benchmark. Delay or Disable Windows Services There’s no real reason to disable Windows services anymore. There was a time when Windows was particularly heavy and computers had little memory — think Windows Vista and those “Vista Capable” PCs Microsoft was sued over. Modern versions of Windows like Windows 7 and 8 are lighter than Windows Vista and computers have more than enough memory, so you won’t see any improvements from disabling system services included with Windows. Some people argue for not disabling services, however — they recommend setting services from “Automatic” to “Automatic (Delayed Start)”. By default, the Delayed Start option just starts services two minutes after the last “Automatic” service starts. Setting services to Delayed Start won’t really speed up your boot time, as the services will still need to start — in fact, it may lengthen the time it takes to get a usable desktop as services will still be loading two minutes after booting. Most services can load in parallel, and loading the services as early as possible will result in a better experience. The “Delayed Start” feature is primarily useful for system administrators who need to ensure a specific service starts later than another service. If you ever find a guide that recommends you set a little-known registry setting to improve performance, take a closer look — the change is probably useless. Want to actually speed up your PC? Try disabling useless startup programs that run on boot, increasing your boot time and consuming memory in the background. This is a much better tip than doing any of the above, especially considering most Windows PCs come packed to the brim with bloatware.     

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  • Developing a feature which sole purpose to be taken out?

    - by adib
    What is the name of the pattern in which individual contributors (programmers/designers) developed an artifact for the sole purpose is to serve as a diversion so that management can remove that feature in the final product? This is a folklore I heard from an ex-colleague who used to work at a large game development company. At that company, it is well known that middle management is pressurized to "give inputs" and "make changes" to the product otherwise they risk being seen as not contributing to the project. This situation have delayed many projects because of these superfluous "management inputs". In one project at the above company, the artists and developers created a supernumerary animated character that appears in every cutscene and sticks out like a sore thumb. They designed it in such a way that it can be easily removed before the game is shipped (this was when games were still sold in physical media and not a downloadable product). Obviously the management then voted to remove the animation. On the positive side, management didn't introduced any unnecessary changes that would have delayed the project because they have shown that they provided constructive inputs to the product. This process pattern has a name among game programmers that work in corporates, but I forgot what was the actual name. I believe it's duck-something. Anybody can help pointing out the name and perhaps some rather credible reference to how the pattern develops?.

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  • Database Replication check script not running

    - by Tarun
    I'm trying to create a Database Replication checking script but I'm getting error while executing it. Here is the script #!/bin/bash PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin export PATH #Server Name Server="Test Server" #My Sql Username and Password User=root Password="a" #Maximum Slave Time Delay Delay="60" #File Path to store error and email the same Log_File=/tmp/replicationcheck.txt #Email Settings Subject="$Server Replication Error" Sender_Name=TestServer Recipients="[email protected]" #Mail Alert Function mailalert(){ sendmail -F $Sender_Name -it <<END_MESSAGE To: $Recipients Subject: $Subject $Message_Replication_Error `/bin/cat $Log_File` END_MESSAGE } #Show Slave Status Show_Slave_Status=`echo "show slave status \G;" | mysql -u $User -p$Password 2>&1` #Getting list of queries in mysql $Show_Slave_Status | grep "Last_" > $Log_File #Check if slave running $Show_Slave_Status | grep "Slave_IO_Running: No" if [ "$?" -eq "0" ]; then Message_Replication_Error="$Server Replication error please check. The Slave_IO_Running state is No." mailalert exit 1 else $Show_Slave_Status | grep "Slave_IO_Running: Connecting" if [ "$?" -eq "0" ]; then Message_Replication_Error="$Server Replication error please check. The Slave_IO_Running state is Connecting." mailalert exit 1 fi fi #Check if replication delayed Seconds_Behind_Master=$Show_Slave_Status | grep "Seconds_Behind_Master" | awk -F": " {' print $2 '} if [ "$Seconds_Behind_Master" -ge "$Delay" ]; then Message_Replication_Error="Replication Delayed by $Seconds_Behind_Master." mailalert else if [ "$Seconds_Behind_Master" = "NULL" ]; then Message_Replication_Error="$Server Replication error please check. The Seconds_Behind_Master state is NULL." mailalert fi fi

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  • When do I use Apache Kafka, Azure Service Bus, vs Azure Queues?

    - by makerofthings7
    I'm trying to understand the situations I'd use Apache Kafka, Azure Service Bus, or Azure Queues for high scale message processing. Which is better for standard Pub Sub situations? Where multiple clients get a copy of the same message? Which is better for low latency Pub sub and no durability? Which is better for "cooperating producer" and "competing consumer"? (what does this mean?) I see a bit of overlap in function between Kafka, Service Bus, Azure Queues

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  • Bukkit inventory saving: crashing somewhere

    - by HcgRandon
    I'm working on a command for a bukkit plugin that lets you transfer worlds. In the section about saving the player's inventory, I'm getting a runtime error. My question is: Why is the error happening, and how can I prevent it? The plugin code public void savePlayerInv(Player p, World w){ File playerInvConfigFile = new File(plugin.getDataFolder() + File.separator + "players" + File.separator + p.getName(), "inventory.yml"); FileConfiguration pInv = YamlConfiguration.loadConfiguration(playerInvConfigFile); PlayerInventory inv = p.getInventory(); int i = 0; for (ItemStack stack : inv.getContents()) { //increment integer i++; String startInventory = w.getName() + ".inv." + Integer.toString(i); //save inv pInv.set(startInventory + ".amount", stack.getAmount()); pInv.set(startInventory + ".durability", Short.toString(stack.getDurability())); pInv.set(startInventory + ".type", stack.getTypeId()); //pInv.set(startInventory + ".enchantment", stack.getEnchantments()); //TODO add enchant saveing } i = 0; for (ItemStack armor : inv.getArmorContents()){ i++; String startArmor = w.getName() + ".armor." + Integer.toString(i); //save armor pInv.set(startArmor + ".amount", armor.getAmount()); pInv.set(startArmor + ".durability", armor.getDurability()); pInv.set(startArmor + ".type", armor.getTypeId()); //pInv.set(startArmor + ".enchantment", armor.getEnchantments()); } //save exp if (p.getExp() != 0) { pInv.set(w.getName() + ".exp", p.getExp()); } } The offending line The stack trace complains about line 130, which is this line. pInv.set(startInventory + ".amount", stack.getAmount()); The stack trace 2012-03-21 13:23:25 [SEVERE] null org.bukkit.command.CommandException: Unhandled exception executing command 'wtp' in plugin Needs v1.0 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42) at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:166) at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:461) at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:818) at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:778) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:761) at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33) at net.minecraft.server.NetworkManager.b(NetworkManager.java:229) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:112) at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78) at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:554) at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452) at net.minecraft.server.ThreadServerApplication.run(SourceFile:490) Caused by: java.lang.NullPointerException at com.devoverflow.improved.needs.commands.CommandWorldtp.savePlayerInv(CommandWorldtp.java:130) at com.devoverflow.improved.needs.commands.CommandWorldtp.onCommand(CommandWorldtp.java:60) at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40) ... 12 more

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  • TechEd 2014 Day 3

    - by John Paul Cook
    There is some confusion about durability of data stored in SQL Server in-memory tables, so some review of the concepts is appropriate. The in-memory option is enabled at the database level. Enabling it at the database level only gives you the option to specify the in-memory feature on a table by table basis. No existing tables or new tables will by default become in-memory tables when you enable the feature at the database level. If you choose to make a table an in-memory table, by default it is...(read more)

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  • Bukkit saving inventory

    - by HcgRandon
    Alright i will make this quick... I am working on a command in my plugin to allow you to transfer worlds and i am trying to save inventory but i am getting a problem here is the code: public void savePlayerInv(Player p, World w){ File playerInvConfigFile = new File(plugin.getDataFolder() + File.separator + "players" + File.separator + p.getName(), "inventory.yml"); FileConfiguration pInv = YamlConfiguration.loadConfiguration(playerInvConfigFile); PlayerInventory inv = p.getInventory(); int i = 0; for (ItemStack stack : inv.getContents()) { //increment integer i++; String startInventory = w.getName() + ".inv." + Integer.toString(i); //save inv pInv.set(startInventory + ".amount", stack.getAmount()); pInv.set(startInventory + ".durability", Short.toString(stack.getDurability())); pInv.set(startInventory + ".type", stack.getTypeId()); //pInv.set(startInventory + ".enchantment", stack.getEnchantments()); //TODO add enchant saveing } i = 0; for (ItemStack armor : inv.getArmorContents()){ i++; String startArmor = w.getName() + ".armor." + Integer.toString(i); //save armor pInv.set(startArmor + ".amount", armor.getAmount()); pInv.set(startArmor + ".durability", armor.getDurability()); pInv.set(startArmor + ".type", armor.getTypeId()); //pInv.set(startArmor + ".enchantment", armor.getEnchantments()); } //save exp if (p.getExp() != 0) { pInv.set(w.getName() + ".exp", p.getExp()); } } Now here is the stack trace i recive it is commplaing about line 130 which is this line pInv.set(startInventory + ".amount", stack.getAmount()); okay now trace 2012-03-21 13:23:25 [SEVERE] null org.bukkit.command.CommandException: Unhandled exception executing command 'wtp' in plugin Needs v1.0 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42) at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:166) at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:461) at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:818) at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:778) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:761) at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33) at net.minecraft.server.NetworkManager.b(NetworkManager.java:229) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:112) at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78) at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:554) at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452) at net.minecraft.server.ThreadServerApplication.run(SourceFile:490) Caused by: java.lang.NullPointerException at com.devoverflow.improved.needs.commands.CommandWorldtp.savePlayerInv(CommandWorldtp.java:130) at com.devoverflow.improved.needs.commands.CommandWorldtp.onCommand(CommandWorldtp.java:60) at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40) ... 12 more

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  • TechEd 2014 Day 3

    - by John Paul Cook
    There is some confusion about durability of data stored in SQL Server in-memory tables, so some review of the concepts is appropriate. The in-memory option is enabled at the database level. Enabling it at the database level only gives you the option to specify the in-memory feature on a table by table basis. No existing tables or new tables will by default become in-memory tables when you enable the feature at the database level. If you choose to make a table an in-memory table, by default it is...(read more)

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  • SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

    - by pinaldave
    This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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  • Query to sum duplicated fields

    - by g0sha
    Here is mysql data id usr good quant delayed cart_ts ------------------------------------------------------ 14 4 1 1 0 20100601235348 13 4 11 1 0 20100601235345 12 4 4 1 0 20100601235335 11 4 1 1 0 20100601235051 10 4 11 1 0 20100601235051 9 4 4 1 0 20100601235051 15 4 2 1 0 20100601235350 16 4 7 1 0 20100602000537 17 4 3 1 0 20100602000610 18 4 3 1 0 20100602000616 19 4 8 1 0 20100602000802 20 4 8 1 0 20100602000806 21 4 8 1 0 20100602000828 22 4 8 1 0 20100602000828 23 4 8 1 0 20100602000828 24 4 8 1 0 20100602000828 25 4 8 1 0 20100602000828 26 4 8 1 0 20100602000829 27 4 8 1 0 20100602000829 28 4 9 1 0 20100602001045 29 4 10 1 0 20100602001046 I need to group fields in witch usr & good has duplicated values with summing quant field for getting smth like this: id usr good quant delayed cart_ts ------------------------------------------------------ 14 4 1 2 0 20100601235348 13 4 11 2 0 20100601235345 12 4 4 2 0 20100601235335 15 4 2 1 0 20100601235350 16 4 7 1 0 20100602000537 17 4 3 2 0 20100602000610 19 4 8 9 0 20100602000802 28 4 9 1 0 20100602001045 29 4 10 1 0 20100602001046 Which MySQL query I need to do to have this effect?

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  • Where are tables in Mnesia located?

    - by Sanoj
    I try to compare Mnesia with more traditional databases. As I understand it tables in Mnesia can be located to: ram_copies - tables are stored in RAM only, so no durability as in ACID. disc_copies - tables are located on disc and a copy is located in RAM, so the table can not be bigger than the available memory? disc_only_copies - tables are located to disc only, so no caching in memory and worse performance? And the size of the table are limited to the size of dets or the table has to be fragmented. So if I want the performance of doing reads from RAM and the durability of writes to disc, then the size of the tables are very limited compared to a traditional RDBMS like MySQL or PostgreSQL. I know that Mnesia aren't meant to replace traditional RDBMS:s, but can it be used as a big RDBMS or do I have to look for another database? The server I will use is a VPS with limited amount of memory, around 512MB, but I want good database performance. Are disc_copies and the other types of tables in Mnesia so limited as I have understood?

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  • CodePlex Daily Summary for Sunday, May 30, 2010

    CodePlex Daily Summary for Sunday, May 30, 2010New ProjectsAviva Solutions C# Coding Guidelines: A set of C# coding guidelines, coding standards, layout rules, FxCop rulesets and (upcoming) custom FxCop and StyleCop rules for improving the over...BKWork: private project.classbook: du an trong vong 10 ngay. Nhom (Do Bao Linh, Phan Thanh Tai, Nguyen Dang Loc)Du an - 01: Du an mon thay LuongEndNote助手: EndNote Helper is a assistant tool for EndNote, which make your task of reference management more convinent. EndNote 助手是一个用于辅助EndNote进行文献管理的小工具,它可...Evoucher: Simple Evoucher Sales SystemFiddler Delayed Responses Extension: A fiddler extension that help developers delay the delivery of HTML Responses to applications. Some delay user stories: - Delivery of css to HTML ...Generic Entity Model 2: GEM2 is lightweight entity framework for building custom business solutions. It enables rapid approach to entity logic design, while offering out o...GY06: 这个是长大工院于2009年发起的项目,因为种种原因没有完成。JoshDOS: JoshDOS is a command line operating system kernel based off COSMOS. It can be booted from actual hardware and built in Visual Studio using .NET la...PhysicsFMUDeluxe.NET: Este projeto é desenvolvido com o intuíto de treinar o desenvolvimento de aplicações em C#. Ele contém ferramentas para cálculos de física e matemá...Reactor Services Platform: Reactor is a service composition and deployment grid that streamlines developing, composing, deploying and managing services. Reactor Services are ...SerafinApartment: Simple MVC 2 application for apartment rental. It is multingual booking system, that allows users to register, book and subscribe for notifications...Silverlight Audio Effect Box: This is a C# Silverlight 4 sample application which process audio sample in near real time. It allows to capture the default audio input device and...Smart Voice: Smart Voice let's you control Skype using your voice. It allows you to write messages, issue phone calls, etc. This application was developed think...WebDotNet - The minimalist web framework inspired by web.py: WebDotNet is an experiment in web frameworks. Inspired by the python web framework, web.py, it is an exercise in extreme minimalism in a framework...New ReleasesAcies: Acies - Alpha Build 0.0.7: Alpha release. Requires Microsoft XNA Framework Redistributable 3.1 (http://www.microsoft.com/downloads/details.aspx?FamilyID=53867a2a-e249-4560-...AdventureWorksLT 2008 Sample Database Script: AdventureWorksLT 2008 R2 DB Script: This script is based on latest download from the Sample database for SQL Server 2008 R2. The original download from the sample is approx 84 MB and ...ASP.NET Wiki Control: Release 1.3.1: - Removed ASP.NET Session dependency. BreadCrumbs will now work with sessions disabled. Can now also share a URL and have the breadcrumb appropriat...Aviva Solutions C# Coding Guidelines: Visual Studio 2010 Rule Sets: Rule Sets targetting different styles of projects.bvcms - Bellevue Church Management System: Source: This source was used to build the latest {church}.bvcms.comCC.Yacht: CC.Yacht 1.0.10.529: This is the initial release of CC.Yacht. Marked as beta since I don't have any testing/feedback beyond that of myself and my wife.Community Forums NNTP bridge: Community Forums NNTP Bridge V14: Release of the Community Forums NNTP Bridge to access the social and anwsers MS forums with a single, open source NNTP bridge. This release has add...Community Forums NNTP bridge: Community Forums NNTP Bridge V15: Release of the Community Forums NNTP Bridge to access the social and anwsers MS forums with a single, open source NNTP bridge. This release has add...Coronasoft Cryostasis scripting engine: CCSE v0.0.1.0 BETA: This is the 0.0.1.0 Beta Release. If you find any bugs Post them as a comment or in the Discussions tabEndNote助手: EndNote助手2.1.0..0: 去除了注册验证机制。Fiddler Delayed Responses Extension: v0.1: Version 0.1 of Fiddler Delayed Responses Extension. See ChangeLog for more information.Generic Entity Model 2: GEM2 build 52510: This is first BETA release of GEM2! Following implementation is still missing from initial plan: Detailed documentation MySQL operational databa...JoshDOS: JoshDOS Souce: This is the souce for the JoshDOS 1.0 OS kernel. You need the COSMOS user kit to use.JoshDOS: Shell Version 1.0: Whats in this download *JoshDOS user kit *JoshDOS VStudio starter kit *JoshDOS documentation Note: You will need the COSMOS user kit to start deve...miniTodo: mini Todo version 0.3: Todo完了時に音が出なかったのを修正Model Virtual Casting - ASPItalia.com: Model Virtual Casting 0.2: Model Virtual Casting 0.2Questa seconda release di ModelVC è corrispondente a quella mostrata in occasione della Real Code Conference 4.0 tenutasi ...PhysicsFMUDeluxe.NET: PhysicsFMUDeluxe.NET - Setup: Primeira versão pública do PhysicsFMUDeluxe.NETSilverlight Audio Effect Box: Echo Box 1.0: First realease - zip contains : web page + xap file :Smart Voice: Smart Voice 0.1: Here is the first alpha release of Smart Voice. Please remember this was done for a curricular unit project at my university and i understand that ...StyleCop Contrib: Custom rules v0.2: This release of the custom rules target StyleCop 4.3.3. Included rules are: Spacing Rules - NoTrailingWhiteSpace - IndentUsingTabs Ordering Rules ...System.ComponentModel.DataAnnotations Contrib: 0.2.46280.0: Built with Visual Studio 2010/.Net 4.0. Compiled from source code changeset 46280.VB Styler: VB Styler Suite V 1.3.0.0: This is the newest version of the VB Styler. Here are the new features. New Imaging ColorPicker A template for getting colors via sliders ColorR...VCC: Latest build, v2.1.30529.0: Automatic drop of latest buildWPF Application Framework (WAF): WPF Application Framework (WAF) 1.0.0.90 RC: Version: 1.0.0.90 (Release Candidate): This release contains the source code of the WPF Application Framework (WAF) and the sample applications. ...XNA Collision Detection: XNA Collision Detection Sample Program: I have coded a compact program which shows the collision detection working, and provides a camera class for rendering and moving the "player." Agai...Most Popular ProjectsRawrWBFS ManagerAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)patterns & practices – Enterprise LibraryMicrosoft SQL Server Community & SamplesPHPExcelASP.NETMost Active ProjectsAStar.netpatterns & practices – Enterprise LibraryCommunity Forums NNTP bridgeBlogEngine.NETGMap.NET - Great Maps for Windows Forms & PresentationIonics Isapi Rewrite FilterRawrCustomer Portal Accelerator for Microsoft Dynamics CRMFacebook Developer ToolkitPAP

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  • Users Sound Off on Droid Android 2.1 Update Delay

    <b>Enterprise Mobile Today:</b> "The delayed Android 2.1 update for the Motorola Droid is starting to tarnish the successful launch of Verizon's first smartphone to run on Google's open source mobile operating system, according to posts at Motorola's Facebook page."

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  • Error ¨Sheduled backup delayed¨ even though network is available

    - by AviD1511
    I get this message every time I bootup the machine Schedule Backup delayed Backup will begin when a network connection becomes available The network is working fine and I can use the internet, also I can manually perform backups. I am a new user & using ubuntu 12.04 precise pangolin. Below is the link of screenshot of the error message(Unable to attach image as a new user). Here is the error message:

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  • How to debug lag using Bluetooth connected mouse and A2DP headset?

    - by gertvdijk
    I own a Logitech M555b mouse (since a week) for use with my HP Elitebook 8570w laptop running Kubuntu 12.04. Works fine right after connecting using the KDE Bluetooth control module. However, after some time (seemingly random), it starts to lag. Movements are being delayed for roughly 500ms for a short period of time. Usually it recovers after some time too, but it can take minutes. All actions are being delayed: movements, click, scrolls. Additionally, the movements can be choppy during these times. A workaround that always works for the same short period of time is to disconnect an re-connect the mouse. This can be done using the same KDE Bluetooth control module. What did I try already? Running this at boot time: echo on > `readlink -f /sys/class/bluetooth/hci0`/../../../power/level To disable any power saving features on the Bluetooth hci0 device. Check the mouse's batteries (it's just a week old, other new batteries: same result) Checking logs and kernel messages about Bluetooth-related entries: none aside the expected messages on connect time. I'm running kernel 3.5.0-13-generic as provided in the xorg-edgers PPA. Booting the regular 3.2 Precise kernel results in the same behaviour. Some other information that may help: It happens when no other Bluetooth connections are active on the machine. Similar symptoms also occur on my Bluetooth stereo (A2DP) headset, but then it's audio lagging and skipping. Swapping Bluetooth profiles as described here then helps. Conclusion: it's not the mouse that's faulty. The headset always worked fine using my now dead Thinkpad T61p with built-in Bluetooth. The bluetooth module in my laptop is connected via USB and shows up as Bus 002 Device 003: ID 0a5c:21e1 Broadcom Corp. I'm mobile and several people around me are using Bluetooth at work (A2DP mostly). It also occurs at home, where my neighbours are probably using Bluetooth as well. It could just be radio interference, but I think Bluetooth connections should just hop to another channel. And, moreover, it just works properly instantly when re-connecting. Therefore I think it's a software driver issue and I'd like to debug it. Is there any way to get more verbose logging on the Bluetooth(-hid) modules?

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  • Droid's Android 2.1 Update Halted

    <b>Enterprise Mobile Today:</b> "Motorola's planned rollout of the Android 2.1 operating system for its popular Droid smartphone has been delayed indefinitely -- with some reports blaming it on the discovery of a serious bug."

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  • A Bit Cloudy

    - by Chris Massey
    "Systems Administrators, I come in peace. You have nothing to fear from me" - Office 365 Microsoft Business Productivity Online Suite recently absorbed a few other services and has been rebranded as Office 365, which is currently in private Beta and NDA-d up to the eyeballs. As Microsoft's (slightly delayed) answer to Google Apps Premier Edition, it shows a lot of promise; MS has technical expertise, market penetration, and financial capital all going for it. On the other hand, Google...(read more)

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  • GNOME 2.30: Waiting for the Big Release

    <b>Datamation:</b> "GNOME 2.30 was originally intended to coincide with GNOME 3.0 -- a massive cleanup and rethinking of the popular desktop. However, GNOME 3.0 is delayed for at least another release, which leaves GNOME 2.30 as most likely the last version in a series stretching back almost a decade."

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  • PASS: FY10 Actuals Posted

    - by Bill Graziano
    Earlier this year we published preliminary fiscal year 2010 financials to the Governance page on the PASS web site.  Please remember that FY10 runs from July 1st, 2009 through June 30th, 2010 and includes the November 2009 Summit.  We do our fiscal year this way so that the Summit falls earlier in the fiscal year.  The financials we had posted were P&L numbers at the portfolio level.  Prior to this we had posted our detailed budget but only posted the auditors report at the end of each year.  Today we updated our published financials to include: Pre-audit actuals from FY10 at the same level as our budget.  The document has both actuals and budget for FY10 side by side.  This is over 20 pages of detailed financial information covering hundreds of line-items. A letter describing key differences between our budget and actuals.  I walked through each line item where the difference was greater than $25,000 and explained what happened and why. We updated the financial graph going back to 2003 to include FY10. This update should “close the loop” on our financials.  You can now start with the published budget and compare it to the finished financials at the same level of detail.  We also plan to publish the auditor’s report when that is completed -- as we do every year. Overall I’m very happy with how FY10 turned out.  Keep in mind that this was the November 2009 Summit so we were still facing economic challenges.  With all that we were roughly break-even showing a $15,000 profit on $3.9 million of revenue.  I didn’t find anything shocking in reviewing our actual vs. budget but there were a few things that needed explanation.  You can see those in the letter on the governance page. Please keep in mind that these are the actuals from our operating financials.  The auditor may have us make adjustments for depreciation or other financial transactions.  We may also account for certain transactions differently for tax purposes than we do for financial reporting purposes.  I feel these financial statements give you the clearest picture of how our organization spends its money. We were late publishing these this year.  We were working through some tax issues and that delayed our ability to file our final tax forms which delayed this process.  In hindsight I should have published these documents as soon as we had them and not waited for the tax issues.  We’ll do this better in the future. And on a final note, you don’t need to login to view these documents.  If you have any questions you can post them here.  If we get more than a few questions we may see about creating some forums for financial issues on the PASS web site.

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  • Problem trying to lock framerate at 60 FPS

    - by shad0w
    I've written a simple class to limit the framerate of my current project. But it does not work as it should. Here is the code: void FpsCounter::Process() { deltaTime = static_cast<double>(frameTimer.GetMsecs()); waitTime = 1000.0/fpsLimit - deltaTime; frameTimer.Reset(); if(waitTime <= 0) { std::cout << "error, waittime: " << waitTime << std::endl; } else { SDL_Delay(static_cast<Uint32>(waitTime)); } if(deltaTime == 0) { currFps = -1; } else { currFps = 1000/deltaTime; } std::cout << "--Timings--" << std::endl; std::cout << "Delta: \t" << deltaTime << std::endl; std::cout << "Delay: \t" << waitTime << std::endl; std::cout << "FPS: \t" << currFps << std::endl; std::cout << "-- --" << std::endl; } Timer::Timer() { startMsecs = 0; } Timer::~Timer() { // TODO Auto-generated destructor stub } void Timer::Start() { started = true; paused = false; Reset(); } void Timer::Pause() { if(started && !paused) { paused = true; pausedMsecs = SDL_GetTicks() - startMsecs; } } void Timer::Resume() { if(paused) { paused = false; startMsecs = SDL_GetTicks() - pausedMsecs; pausedMsecs = 0; } } int Timer::GetMsecs() { if(started) { if(paused) { return pausedMsecs; } else { return SDL_GetTicks() - startMsecs; } } return 0; } void Timer::Reset() { startMsecs = SDL_GetTicks(); } The "FpsCounter::Process()" Method is called everytime at the end of my gameloop. I've got the problem that the loop is correctly delayed only every second frame, so it runs one frame delayed at 60 FPS and the next without delay at over 1000 fps. I am searching the error quite a while now, but I do not find it. I hope somebody can point me in the right direction.

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  • tcp msl timeout

    - by iamrohitbanga
    The following is given in the book TCP IP Illustrated by Stevens Quiet Time Concept The 2MSL wait provides protection against delayed segments from an earlier incarnation of a connection from being interpreted as part of a new connection that uses the same local and foreign IP addresses and port numbers. But this works only if a host with connections in the 2MSL wait does not crash. What if a host with ports in the 2MSL wait crashes, reboots within MSL seconds, and immediately establishes new connections using the same local and foreign IP addresses and port numbers corresponding to the local ports that were in the 2MSL wait before the crash? In this scenario, delayed segments from the connections that existed before the crash can be misinterpreted as belonging to the new connections created after the reboot. This can happen regardless of how the initial sequence number is chosen after the reboot. To protect against this scenario, RFC 793 states that TCP should not create any connections for MSL seconds after rebooting. This is called the quiet time Few implementations abide by this since most hosts take longer than MSL seconds to reboot after a crash. Do operating systems wait for 2MSL seconds now after a reboot before initiating a TCP connection. The boot times are also less these days. Although the ports and sequence numbers are random but is this wait implemented in Linux?

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  • tcp msl timeout implementation in linux

    - by iamrohitbanga
    The following is given in the book TCP IP Illustrated by Stevens Quiet Time Concept The 2MSL wait provides protection against delayed segments from an earlier incarnation of a connection from being interpreted as part of a new connection that uses the same local and foreign IP addresses and port numbers. But this works only if a host with connections in the 2MSL wait does not crash. What if a host with ports in the 2MSL wait crashes, reboots within MSL seconds, and immediately establishes new connections using the same local and foreign IP addresses and port numbers corresponding to the local ports that were in the 2MSL wait before the crash? In this scenario, delayed segments from the connections that existed before the crash can be misinterpreted as belonging to the new connections created after the reboot. This can happen regardless of how the initial sequence number is chosen after the reboot. To protect against this scenario, RFC 793 states that TCP should not create any connections for MSL seconds after rebooting. This is called the quiet time Few implementations abide by this since most hosts take longer than MSL seconds to reboot after a crash. Do operating systems wait for 2MSL seconds now after a reboot before initiating a TCP connection. The boot times are also less these days. Although the ports and sequence numbers are random but is this wait implemented in Linux? Also RFC 793 says that this wait is not required if history is maintained. Does linux maintain any history of used sequence numbers for connections to handle this case?

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  • One workstation gets slow access to the server, but others are fast

    - by Mike Hanson
    I've just setup a machine with Windows Server 2008. It hosts various services, like IIS, POP3, SMTP, Music for Squeezeboxes, VNC. All was working well for the first week or so. One day I needed to create a mapped drive on the server, so it could access files on my workstation. Windows indicated that Network Discovery was needed, so I turned it on with the "Home / Office" option (rather than "Public"). This may be coincidence, but since that time I've been having troubles accessing various services from my main workstation (running Windows 7/64): POP3 continued working correctly, but SMTP was delayed or failed entirely. (Telnet took 20 seconds to connect, but Outlook would never send messages.) VNC failed entirely. I reinstalled it on the server, and now it works but feels sluggish. The music web server was extremely delayed and usually failed. I tried reinstalling, and now it takes about 30 seconds to show the page name on the browser tab, and another 30 seconds to display any page contents. Other machines on the local network seem fine, as do machines connected via the Internet. I don't believe I changed anything on my own machine that would cause this. I considered the possibility that my anti-virus was involved, so I uninstalled AVG (commercial version), but that didn't help. I installed Norton 360 after that, and it didn't complain of viruses on my machine, and the delays remained. Because only my machine is affect, I'm tempted to blame it, except that reinstalling software on the server improved the situation, so there is almost certainly something going on with the server too. The firewall has all the necessary ports open, and it works fine for the other workstations (including external machines connected via the Internet), which indicates that it should be OK. Any ideas?

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