Reserve memory for critical activities

You can reserve a specific amount of memory for use when critical activities (such as rollback activities) are required and the database server has limited free memory. This prevents the database server from crashing if the server runs out of free memory during critical activities.

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 a user is getting out of memory errors. If the value of LOW_MEMORY_RESERVE is 0, the low memory reserve functionality is turned off.

For example, 512 kilobytes is a reasonable amount of reserved memory. To reserve 512 kilobytes, specify:

LOW_MEMORY_RESERVE 512

You can also use the onmode -wm or onmode -wf command to dynamically adjust the value of the LOW_MEMORY_RESERVE configuration parameter.

Use the onstat -g seg command to monitor the LOW_MEMORY_RESERVE value. Look for the last two lines of output, which contain the phrase "low memory reserve." The first of these output lines shows the size of memory reserved in bytes. The second of these lines shows the number times that the database server has used this memory and the maximum memory required. Both of these values are reset when the server is restarted.


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