Resident portion of shared memory

The resident portion of shared memory includes areas of shared memory that record the state of the database server, including locks, log files, and the locations of dbspaces, chunks, and tblspaces.

The settings that you use for the LOCKS, LOGBUFF, and PHYSBUFF configuration parameters help determine the size of the resident portion.

In addition to these configuration parameters, which affect the size of the resident portion, the RESIDENT configuration parameter can affect memory use. When a computer supports forced residency and the RESIDENT configuration parameter is set to a value that locks the resident or resident and virtual portions, the resident portion is never paged out.

The machine notes file for your database server indicates whether your operating system supports forced residency.

On AIX®, Solaris, and Linux systems that support large pages, the IFX_LARGE_PAGES environment variable can enable the use of large pages for non-message shared memory segments that are locked in physical memory. If large pages are configured by operating system commands and the RESIDENT configuration parameter specifies that some or all of the resident and virtual portions of shared memory are locked in physical memory, Informix® uses large pages for the corresponding shared memory segments, provided sufficient large pages are available. The use of large pages can offer significant performance benefits in large memory configurations.

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