Linux kernel settings for the DB2 Universal Database system

The kernel semaphore settings recommended for DB2® are used. To use these settings, the kernel.sem setting is placed in the file /etc/sysctl.conf.

kernel.sem=”250 32000 32 4096”

The values in this line are:

• The first value is the number of semaphores per array: 250.
• The second value is the maximum number of semaphores system wide: 32000.
• The third value is the maximum number of operations per semop call: 32.
• The fourth value is the maximum number of semaphore arrays: 4096.

The use of these values also implies a maximum number of system-wide semaphores, which is calculated by multiplying the maximum number of semaphore arrays by the number of semaphores per array (4096 multiplied by 250). In this case, the value for system wide semaphores was capped at 32 000.

This setting is activated automatically at system start time when the boot.sysctl service is enabled, or at run time by issuing this command:

sysctl -p /etc/sysctl.conf