How to Increase Shared Memory Segments

1. Open the /etc/system file, using the editor of your choice.

2. Add the following variables to increase shared memory segments.

   set shmsys:shminfo_shmmax=value set shmsys:shminfo_shmmin=value set shmsys:shminfo_shmmni=value set shmsys:shminfo_shmseg=value set semsys:seminfo_semmap=value set semsys:seminfo_semmni=value set semsys:seminfo_semmns=value set semsys:seminfo_semmsl=value set semsys:seminfo_semmnu=value set semsys:seminfo_semume=value

   shmsys:shminfo_shmmax	Maximum shared memory segment size
   shmsys:shminfo_shmmin	Mininum shared memory segment size
   shmsys:shminfo_shmmni	Number of shared memory identifiers
   shmsys:shminfo_shmseg	Number of segments, per process
   semsys:seminfo_semmap	Number of entries in the semaphore map
   semsys:seminfo_semmni	Number of semaphore identifiers
   semsys:seminfo_semmns	Number of semaphores in the system
   semsys:seminfo_semmsl	Maximum number of semaphores, per id
   semsys:seminfo_semmnu	Number of processes using the undo facility
   semsys:seminfo_semume	Maximum number of undo structures per process

3. Exit the file, saving changes.

4. Verify the shared memory value changes.

   # grep shmsys /etc/system

5. Reboot the system.

Example--Increasing Shared Memory Segments

The following shared memory values accommodate a system with a large amount of memory (for example, 128 MBytes) that is running a large database application.

set shmsys:shminfo_shmmax=268435456
set shmsys:shminfo_shmmin=200
set shmsys:shminfo_shmmni=200
set shmsys:shminfo_shmseg=200
set semsys:seminfo_semmap=250
set semsys:seminfo_semmni=500
set semsys:seminfo_semmns=500
set semsys:seminfo_semmsl=500
set semsys:seminfo_semmnu=500
set semsys:seminfo_semume=100