DB2 Server for VM: System Administration

Virtual Storage Requirements

All DB2 Server for VM operations are serviced by database machines. A database machine is a virtual machine in which the system code (the components of the database manager) runs.

Database Machine Size

The amount of virtual storage required by the database machine depends on several factors. The dominant ones are the sizes of the buffer pools (used for the directory and the data), the number of concurrent users to be supported, the complexity of the SQL requests, and the definition of the database. If only the base code has been installed, 8 megabytes are required for the database machine; if the DRDA code has been installed as well, 10 megabytes are required.

If you have coded any date or time exit routines, the size of these routines must be added to the minimum virtual storage. For more information, see Defining Your Own Datetime Format. ISQL cannot be run in the database machine.

If you plan to run the database manager in single user mode, add the size of the application being run, and the resource adapter. See Table 1 for more information on virtual storage requirements. For a description of resource adapter, see How the ARIUXIT Module Works.

The database manager (as a default) runs in the user free storage area. (The entire user program area is used for user free storage when the database manager is running.)

For detailed formulas for calculating virtual storage requirements, see Appendix A, Virtual and Real Storage Requirements.

Service Machine Size

If CMS is defined as a saved segment, a 1-megabyte machine size is recommended; if not, ensure that you define enough virtual storage for the service machine to run CMS. For information on saved segments and how they are defined see Defining Saved Segments.

The service machine does not perform any processing. Its purpose is to own the database manager minidisks so that SQL users can access the IBM-supplied programs, such as ISQL, the DBS utility, and the preprocessors.

User Machine Size

Table 1 shows the recommended increase to virtual storage requirements for a user machine. A 6-megabyte machine size is recommended.

Table 1. Recommended Virtual Storage Increase for User Machine

DB2 Server for VM Component	Recommended Minimum Virtual Storage Increase for a User Virtual Machine (in Kilobytes)
Resource adapter     ISQL     DBS utility     Any DB2 Server for VM preprocessor (PL/I, Assembler, COBOL, FORTRAN, or C)   User program	277 (if base code installed) 2048 (if DRDA code installed)   320 + resource adapter = 597 (base) 320 + resource adapter = 2368 (DRDA)   220 + resource adapter = 497 (base) 220 + resource adapter = 2268 (DRDA)   234 + resource adapter = 511 (base) 234 + resource adapter = 2282 (DRDA)       User application size + resource adapter

To these minimum amounts, add the following amount of storage as needed:

• The values in Table 1 assume that national language message repositories are in saved segments. For each such repository not in a saved segment, add 250 kilobytes. If you use CMS work units, also add 5 kilobytes for the second and each subsequent CMS work unit used by the application.
• Add the size of CMS to these amounts if it is not defined as a saved segment.
• For user programs that use the SQLDS protocol, if the fetch and insert blocking option is in effect, add 8 kilobytes for each currently open cursor that qualifies for blocking.
• For user programs that use the DRDA protocol, add the query block size for each open cursor. (For information on the SQLINIT query block size parameter, see the DB2 Server for VSE & VM Database Administration manual.)
• If you have coded an exit, such as an accounting or a cancel exit, add the size of your routine.