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Database Server System Requirements

From the point of view of the operating system, a database server requires the system resources described in the following sections.

Physical Memory

The amount of physical memory used by the database server process is determined by parameters in the local database definition, see The Local Database, whose initial default values are determined by looking at the amount of installed memory.

VMS: For a database server running on an OpenVMS node the amount of physical memory used by the database server process will vary between the OpenVMS process parameters WSQUOTA and WSEXTENT.
The WSQUOTA parameter is calculated by MIMCONTROL and is set large enough to include the bufferpool, initial SQLPOOL, communication buffers, code, and stack data.
The WSEXTENT parameter is set to the SYSGEN parameter WSMAX (the maximum amount of physical memory a single process may have).
For large buffer pools, it is recommended that a resident memory reservation created in VMS. Please see the Mimer SQL OpenVMS Guide.

Virtual Memory

The amount of virtual memory that the database server process can use is limited by the operating system.

UNIX: The virtual memory handling on Unix platforms is platform specific - refer to the documentation for the specific Unix operating system you are using. (Often a paging file used).

VMS: The MIMCONTROL command sets the paging file quota of the database server so that it is large enough to contain all memory areas, including the bufferpool and an SQLPOOL that has grown to MaxSQLPool kilobytes.
It may be appropriate to create larger page files to increase the amount of virtual memory available to the database server.
Note that if the buffer pool does not use the page files if it is placed in a resident memory reservation.

Win: If you get a message saying the system is running out of virtual memory you may need to increase the size of your paging file. This done by using the Virtual Memory option in the Performance section of the System control panel.

Global Pages

VMS: The database server creates a global section for its communication buffers. This global section resides on the page file. The amount of memory a global section may take from a page file is generally controlled by an operating system parameter. If this limit set by the operating system is exceeded, the MIMCONTROL/START command will fail with the message:
%SYSTEM-E-EXGBLPAGFIL, exceeded global page file limit

If this happens, the OpenVMS SYSGEN parameter called GBLPAGFIL, which limits the amount of memory that global sections may take from the page files, should be increased.

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