Tunning AIX for websphere

luweinet

Tuning AIX systems
This topic describes how to tune the AIX operating system to optimize the performance of your WebSphere Application Server.
About this task
There are a number of configuration changes and variables you can set to tune the performance of Websphere to suit your needs. Because the AIX operating system is not a WebSphere Application Server product, be aware that it can change and results can vary.
Procedure
Change the following configuration settings or variables according to your needs:
    * TCP_TIMEWAIT
          o Description: Determines the time that must elapse before TCP/IP can release a closed connection and reuse its resources. This interval between closure and release is known as the TIME_WAIT state or twice the maximum segment lifetime (2MSL) state. During this time, reopening the connection to the client and server costs less than establishing a new connection. By reducing the value of this entry, TCP/IP can release closed connections faster, providing more resources for new connections. Adjust this parameter, if the running application requires rapid release or the creation of new connections, or if a low throughput occurs due to many connections sitting in the TIME_WAIT state.
          o How to view or set:
            Issue the following command to set TCP_TIMEWAIT state to 15 seconds:
            /usr/sbin/no –o tcp_timewait =1
    * AIX operating systems with DB2
          o Description: Separating your DB2 log files from the physical database files can boost performance. You can also separate the log and the database files from the drive that contains the Journaled File System (JFS) service. AIX uses specific volume groups and file systems for the JFS logging.
          o How to view or set: Use the AIX filemon utility to view all the file system input and output and to strategically select the file system for the DB2 log files. Set the DB2 log location according to the DB2 tuning parameters topic.
          o Default value: The default location for the DB2 log files is often the same disk drive where the database tables are stored.
          o Recommended value: Move the files to a disk that is separate from the DB2 data and has the minimum input or output activity.
    * AIX file descriptors (ulimit)
          o Description: Specifies the various restrictions on resource usage on the user account. The ulimit -a command displays all the ulimit limits. The ulimit -a command specifies only the number of open files that are permitted. The default number of open files setting (2000) is typically sufficient for most applications. If the value set for this parameter is too low, errors might occur when opening files or establishing connections. Because this value limits the number of file descriptors that a server process might open, a value that is too low prevents optimum performance.
          o How to view or set: Perform the following steps to change the open file limit to 10,000 files:
               1. Open the command window.
               1. Edit the /etc/security/limits file. Add the following lines to the user account that the WebSphere Application Server process runs on:
                  nofiles =  10000
                  nofiles_hard = 10000
               2. Save the changes.
               3. Restart your AIX system.
               4. To verify the result, type the ulimit -a command on the command line. For example, type # ulimit -a.
          o Default value: For the AIX operating system, the default setting is 2000.
          o Recommended value: The value is application dependent. Increasing the ulimit file descriptor limits might improve performance. Increasing some of the other limits might be needed depending on your application. Any changes to the data or stack ulimits should ensure that data+stack  Application Servers > server_name.
               2. Under Server Infrastructure, click Java and Process Management > Process Definition > Java Virtual Machine.
               3. In the Generic JVM Argument field, add -Xlp.
         5. Add the EXTSHM custom property and set to OFF.
               1. Click Servers > Application Servers > server_name.
               2. Under Server Infrastructure, click Java and Process Management > Process Definition > Custom properties > New.
               3. In the Name field, enter EXTSHM.
               4. In the Value field, enter OFF.
         6. Validate large page support is used with the following command:
            vmstat  -l  1
            Note: The "alp" column is non-zero when the application is running.
      There are several concerns when enabling large pages, which can cause serious events to occur on the machine when large pages are enabled. For more information on AIX large pages, see the "Considerations for using large pages" section at the following address: http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.prftungd/doc/prftungd/large_page_ovw.htm.
      If you do not want to use the large pages option, there is also a medium page option. The medium page size option, which is similar, and has close to the same performance gains as large pages. However, it does not involve the problems of reserving physical memory for a specific user or process. For more information, see the -Xlp64k option in the Tuning Java virtual machines topic.
    * Other AIX information
      Consider the other AIX operating system settings that are not within the scope of this document. You can adjust the following additional settings:
          o Adapter transmit and receive queue
          o TCP/IP socket buffer
          o IP protocol mbuf pool performance
          o Update file descriptors
          o Update the scheduler
      For more information about AIX operating systems, see Performance: Resources for learning.
               
               
               

本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/6408/showart_1102000.html