Setting Shmmni Parameter; Setting Shmall Parameter - Red Hat ENTERPRISE LINUX 5.1 - LINUX ORACLE Tuning Manual

Chapter 7. Setting Shared Memory
# cat /proc/sys/kernel/shmmax
2147483648
The default shared memory limit for SHMMAX can be changed in the proc file system without reboot:
# echo 2147483648 > /proc/sys/kernel/shmmax
Alternatively, you can use sysctl(8) to change it:
# sysctl -w kernel.shmmax=2147483648
To make a change permanent, add the following line to the file /etc/sysctl.conf (your setting may
vary). This file is used during the boot process.
# echo "kernel.shmmax=2147483648" >> /etc/sysctl.conf

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

7.3. Setting SHMALL Parameter

This parameter sets the total amount of shared memory pages that can be used system wide. Hence,
SHMALL should always be at least ceil(shmmax/PAGE_SIZE).
The default size for SHMALL in Red Hat Enterprise Linux 2.1, 3, 4 and 5 is 2097152 which is also
Oracle's recommended minimum setting for 9i and 10g on x86 and x86-64 platforms. In most cases
this setting should be sufficient since it means that the total amount of shared memory available on the
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