Configuration Guides › SOA Agent for Web Servers Guide › Operating System Tuning › Tune the Shared Memory Segments

Tune the Shared Memory Segments

If you install an Apache or Oracle iPlanet Web Agent on Solaris systems, you must tune the operating system’s shared memory settings for the Web Agent to function correctly. By increasing the operating system’s shared memory segments, you improve the performance of the Web Agent. The variables that control shared memory segments are defined in the operating system’s specification file.

For AIX operating systems, you must run the following command before starting an Apache server:

export EXTSHM=ON

Note: You may need to tune the shared memory segments if you are using Linux. For more information about the shared memory segments and how to tune them, see the documentation for your particular operating system.

To increase shared memory segments

1. Follow the appropriate procedure for your operating system:
   • Solaris: Open the /etc/system file, using the editor of your choice.
2. Modify the shared memory variables using one of the following methods:
   • Solaris: Add the variables shown in the following list and configure them using the recommended settings shown in the examples. Use the following syntax:

     set shmsys:shminfo_shmmax=33554432
     

   shmsys:shminfo_shmmax

   Specifies the maximum shared memory segment size. Controls the maximum size of the Agent resource and session cache.

   Note: To estimate the amount of memory segments required, allocate 4KB/entry in each cache, or view cache usage statistics in the OneView Monitor. See the Web Agent Configuration Guide for more information about using the OneView Monitor.

   Example: 33554432 (32 mb) for busy sites that need large cache capacity.

   shmsys:shminfo_shmmin

   (Not required for Solaris) Minimum shared memory segment size. Controls the minimum size of the Agent resource and session cache.

   shmsys:shminfo_shmmni

   Specifies the maximum number of shared memory segments that can exist simultaneously, system-wide.

   Example: (except Solaris 9) N/A

   Example: (Solaris 9) 200

   shmsys:shminfo_shmseg

   (Not required for Solaris 9) Specifies the maximum number of shared memory segments per process.

   Example: 24

   semsys:seminfo_semmni

   Specifies the number of semaphore identifiers. Use 11 for every instance of the Agent that you run on the system.

   Example: (except Solaris 9) 100

   Example: (Solaris 9) 200

   semsys:seminfo_semmns

   Specifies the number of semaphores in the system. Use 10 for every instance of the Agent that you run on the system.

   Example: (Solaris 9) 100

   Example: (Solaris 9) 400

   semsys:seminfo_semmnu

   Specifies the number of processes using the undo facility. For optimal performance, semmnu should be greater than the number of Apache child processes or Oracle iPlanet web server processes running on the system at any one time. For Apache servers, this value should exceed the maxclients setting by 200 or more. For Oracle iPlanet web servers, this value should exceed the maxprocs setting by 200 or more.

   Example: (Solaris 9) 200

   Example: (Solaris 9) 400

3. Save your changes then exit the file or the utility.
4. Reboot the system.
5. Verify your changes by entering the command:

   $ sysdef -i