Shared memory and semaphore resource requirements

This topic contains the following sections:

Shared memory and semaphore resource requirements for collecting data on UNIX systems

The Perform Agent and the Collect programs require semaphores and shared memory segments on all computers. BMC TrueSight Capacity Optimization collectors require one semaphore and one shared memory segment for each metric group per instance and each collector per instance.

Resource limits can be set to low values on your system, particularly on Solaris. This setting can be an issue, especially if an application is running on the same node, because application systems also use these resources. See your system administrator for help in setting semaphore and memory segment parameters.

Shared memory and semaphore resources requirements for collecting data on Oracle Solaris systems

On Solaris, you can reconfigure these values without recompiling the kernel by editing the /etc/system file. All entries in /etc/system must be fewer than 80 characters; otherwise, they might disable the kernel.


These changes alter the kernel settings; restart the system for the changes to take effect.

BMC recommends that you reset these values after installation. The values in the /etc/system entry column represent a default system configuration installation. Increasing these limits does not incur any additional overhead, because they are used only when required. If your system is already set to higher values, increase the values by an amount corresponding to the increase shown in the table.

Setting boot time values for shared memory and semaphore parameters

When setting shared memory and semaphore parameters, you must increase the boot time value if it is less than the recommended number. To evaluate whether you must increase the parameter's boot time value, use the guidelines in the following table. 

For additional information about setting boot time values, refer to the "What are the recommended shared memory settings for PATROL Perform? (ID: 15104702)" topic on the BMC Support website Resolution Knowledge Database page.


An instance can be a system or an application collector. In any formula referenced in the "Do This..." column in the following table, 'number of instances' refers to the number of system and application collectors running on a computer. For example, on a computer with one system collector 'number of instances' is one, while on a computer with a system collector and two application collectors, 'number of instances' is three.

Settings for the /etc/system file

For parameter

Which is

Do this


IPC semaphores

semsys: seminfo_semmni

Number of semaphore identifiers (semaphore sets), systemwide.

Add (25 + 25 x the number of instances) to the current value.

If the current value of the computer is 100 and you will be running one system collector, set the value to 150.

semsys: seminfo_semmsl

Maximum number of semaphores per unique identifier.

No specific recommendation. BMC TrueSight Capacity Optimization will attach two semaphores per identifier.

semsys:seminfo_semmsl should remain at its current value.

semsys: seminfo_semopm


No specific recommendation. This semaphore setting has no impact on the operation of BMC TrueSight Capacity Optimization.

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