The RESIDENT configuration parameter and memory utilization

The RESIDENT configuration parameter specifies whether shared-memory residency is enforced for the resident portion of database server shared memory. This configuration parameter works only on computers that support forced residency.

The resident portion in the database server contains the buffer pools that are used for database read and write activity. Performance improves when these buffers remain in physical memory.

You should set the RESIDENT parameter to 1. If forced residency is not an option on your computer, the database server issues an error message and ignores this configuration parameter.

On machines that support 64-bit addressing, you can have a very large buffer pool and the virtual portion of database server shared memory can also be very large. The virtual portion contains various memory caches that improve performance of multiple queries that access the same tables (see Configure and monitor memory caches). To make the virtual portion resident in physical memory in addition to the resident portion, set the RESIDENT parameter to -1.

If your buffer pool is very large, but your physical memory is not very large, you can set RESIDENT to a value greater than 1 to indicate the number of memory segments to stay in physical memory. This specification makes only a subset of the buffer pool resident.

You can turn residency on or off for the resident portion of shared memory in the following ways:
  • Use the onmode utility to reverse temporarily the state of shared-memory residency while the database server is online.
  • Change the RESIDENT parameter to turn shared-memory residency on or off the next time that you start database server shared memory.

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