7.2. Setting SHMMNI Parameter

This parameter sets the system wide maximum number of shared memory segments.

Oracle recommends SHMMNI to be at least 4096 for Oracle 10g. For Oracle 9i on x86 the recommended minimum setting is lower. Since these recommendations are minimum settings, it is best to set it always to at least 4096 for 9i and 10g databases on x86 and x86-64 platforms.

To determine the system wide maximum number of shared memory segments, run:

# cat /proc/sys/kernel/shmmni
4096

The default shared memory limit for SHMMNI can be changed in the proc file system without reboot:

# echo 4096 > /proc/sys/kernel/shmmni

Alternatively, you can use sysctl(8) to change it:

# sysctl -w kernel.shmmni=4096

To make a change permanent, add the following line to the file /etc/sysctl.conf. This file is used during the boot process.

# echo "kernel.shmmni=4096" >> /etc/sysctl.conf