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Memory Guidelines for Dynamic Query Mode

Question & Answer


Question

This document provides general recommendations for the amount of memory that should be allocated for the Java Virtual Machine (JVM) heap associated with dynamic query mode (DQM).

Answer

Although the dynamic query mode (DQM) is supported in 32 bit installations of IBM Cognos BI servers, 64 bit servers are recommended for DQM.

The initial size and size limit of the JVM heap for DQM can be set in Cognos Administration on the Settings tab of the QueryService (steps). By default each of these are set to 1 GB.

In production environments where Cognos dynamic cubes are not employed, it is recommended to set the initial heap size to 4 GB and the limit to 8 GB (a 64 bit server is required for memory settings above 2GB), and then monitor system resource usage during peak hours and adjust the settings accordingly.

Depending on the resources available, these can be raised to much higher values. There are cases where 32 GB and even 64 GB have been appropriate, but only when the hardware accommodates this, otherwise the system will become unstable.

For a server that is operating one or more Cognos dynamic cubes, the size limit of the query service should be set in accordance to the Dynamic Cubes hardware sizing recommendations.

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Document Information

Modified date:
15 June 2018

UID

swg22000066