LOW_MEMORY_RESERVE configuration parameter

Use the LOW_MEMORY_RESERVE configuration parameter to reserve a specific amount of memory for use when critical activities are needed and the server has limited free memory.

If you enable the new LOW_MEMORY_RESERVE configuration parameter by setting it to a specified value in kilobytes, critical activities, such as rollback activities, can complete even when you receive out-of-memory errors.

onconfig.std value
LOW_MEMORY_RESERVE 0
values
0 or 128 - 2147483648, although the maximum value cannot be higher than 20 percent of the value of the SHMVIRTSIZE configuration parameter
units
kilobytes
takes effect
After you edit your onconfig file and restart the database server.
When you reset the value dynamically in your onconfig file by running the onmode -wf command.
When you reset the value in memory by running the onmode -wm command.

Usage

No matter how the LOW_MEMORY_RESERVE configuration parameter is set, the maximum size of reserved memory is 20 percent of the value of the SHMVIRTSIZE configuration parameter.

For example, to reserve 512 kilobytes of memory, specify:
LOW_MEMORY_RESERVE 512

You can use the onstat -g seg command to view low-memory reserve information. The output includes lines that show the size of reserved memory, the number of times that the server has used the reserved memory, and the maximum memory needed.


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