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.

Note

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.

Note

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

Example

IPC semaphores

semsys: seminfo_semmns

Number of semaphore identifiers, systemwide.

Add (50 + 50 x the number of instances) to the current value.

If the current value on the computer is 100 and you have one system agent and one application agent running on the computer, then set the value to 250.

Note: BMC TrueSight Capacity Optimization allocates two semaphores per ID so use 50 instead of 25. Obsolete in Solaris 10 and later.

semsys: seminfo_semmap

Number of entries in the semaphore map.

Set equal to semsys:seminfo_semmni + two.

If semsys: seminfo_semmni was set to 256, set semsys: seminfo_semmap equal to 258.

Note: This is obsolete in Solaris 8 and later.

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_semmnu

Maximum number of undo structures, systemwide.

No specific recommendation. BMC TrueSight Capacity Optimization does not use undo structures.

As a general rule, you might want to set seminfo_semmnu equal to seminfo_semmni to provide for an undo structure for each semaphore. Obsolete in Solaris 10 and later.

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 seminfo_semume seminfo_semvmx seminfo_semaem

 

No specific recommendation. These four semaphore settings have no impact on the operation of BMC TrueSight Capacity Optimization.

Note: seminfo_semume, seminfo_semvmx, and seminfo_semaem are obsolete in Solaris 10 and later.

IPC Shared Memory

shmsys: shminfo_shmmax

Maximum size of a shared memory segment.

Change the setting to a value large enough to hold data for the existing processes running on the system, plus some room for future growth.

Best practice for BMC TrueSight Capacity Optimization is a value of 4294967295 for shminfo_shmmax.

Note: Obsolete in Solaris 10 and later.

shmsys: shminfo_shmmin

Minimum size of an IPC shared memory segment that can be created.

BMC recommends using the system default of 1.

shmsys:shminfo_shmmni should always be set to 1.

Note: Obsolete in Solaris 9 and later.

shmsys: shminfo_shmmni

System wide limit on the number of shared memory segments.

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.

Note: Obsolete in Solaris 10 and later.

shmsys: shminfo_shmseg

Limit on the number of shared memory segments that one process can create.

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.

Note: This is obsolete in Solaris 9 and later.

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