Resident portion of shared memory

The operating system, as it switches between the processes that run on the system, normally swaps the contents of portions of memory to disk. When a portion of memory is designated as resident, however, it is not swapped to disk. Keeping frequently accessed data resident in memory improves performance because it reduces the number of disk I/O operations that would otherwise be required to access that data.

The database server requests that the operating system keep the virtual portions in physical memory when the following two conditions exist:
  • The operating system supports shared-memory residency.
  • The RESIDENT parameter in the onconfig file is set to -1 or a value that is greater than 0.
Warning: You must consider the use of shared memory by all applications when you consider whether to set the RESIDENT parameter to -1. Locking all shared memory for the use of the HCL Informix® database server can adversely affect the performance of other applications, if any, on the same computer.

The resident portion of the database server shared memory stores the following data structures that do not change in size while the database server is running:

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