Defining VSAM buffer pools

Related reading: For overview information, refer to IMS buffer pools.

One or more VSAM local shared resource pools can be defined through the subpool definition statement POOLID. One POOLID statement is specified for each shared resource pool. The POOLID statement must be followed by one or more VSRBF subpool definition statements, which define the subpools within that shared pool.

POOLID control statements

The buffer fix and string number parameters must be separated by commas and coded without intervening blanks. They can be coded in any order. If any parameter is invalid, the remainder of the statement is ignored and defaults apply for the remaining parameters.

The POOLID buffer fix and string number values override the VSAMFIX and STRINGMX parameters on the OPTIONS statement for that particular shared pool.

POOLID=

Required keyword for VSAM shared resource pool definition. It must begin in the first position of the control statement. Only one set of subparameters can be entered for each control statement. Each statement defines one shared resource pool. The POOLID statement is used with the DBD statement to direct a given data set to a specific shared resource pool.

Only the first VSAM local shared resource pool defined with the POOLID statement can contain VSAM subpool definition statements (VSRBF) for subpools not dedicated to specific data sets. All VSAM local shared resource pools defined after the first pool must be dedicated to specific data sets. Add a DBD statement that defines which data sets use the shared resource pool. Therefore, defining a VSAM local shared resource pool other than the first pool defined, without a DBD statement referencing that pool, results in a failure for the POOLID statement.

POOLIDs 0 and 1-254 can be used. The total number of POOLIDs must not exceed 255. Also see the paragraph under RESVPOOL=.

id

A one- to four-character alphanumeric field that specifies a user identifier assigned to a shared resource pool. This parameter is required. It is used with the DBD statement to direct a given data set to a specific shared pool.

FIXDATA=YES│NO

Specifies the data shared resource pool long-term-page-fixing option. If YES is specified, all buffers in the data shared resource pool are long-term-page-fixed at initialization of the shared resource pool. If NO is specified, no buffers in the data shared resource pool are long-term-page-fixed. If this parameter is omitted, the default is NO.

FIXINDEX=YES│NO

Specifies the index shared resource pool long-term-page-fixing option. If YES is specified, all buffers in the index shared resource pool are long-term-page-fixed at initialization of the shared resource pool. If NO is specified, no buffers in the index shared resource pool are long-term-page-fixed. If this parameter is omitted, the default is NO.

FIXBLOCK=YES│NO

Specifies the I/O-related control blocks long-term-page-fixing option. If YES is specified, all I/O-related control blocks are long-term-page-fixed at initialization of the shared resource pool. If NO is specified, no I/O-related control blocks are long-term-page-fixed. If this parameter is omitted, the default is NO.

STRINGNM=n

Specifies the maximum number of VSAM I/O requests that can be concurrently active. It can be used to override the MAXREGN parameter specified at system definition time and the PST value on the EXEC statement. The specified value must be a decimal number 1 - 255. The default is 255. Specify a number as close as possible to the maximum number of regions expected to be running concurrently, including those regions that can be dynamically started. If the value is omitted or invalid, the default is the MAXREGN value or the PST value, which, if present, overrides the MAXREGN value.

RESVPOOL control statements

RESVPOOL=shared-pool-number

The shared-pool-number variable represents the VSAM local shared resource pool number of the shared pool that IMS cannot use. One or more numbers 1 - 254 can be specified in any order and must be separated by commas, but without any blanks. Shared resource pool 0 is reserved for IMS and you cannot use it. A blank must follow the last number specified, and the remaining portion of the statement is not examined.

The RESVPOOL statement is only applicable if you have a product other than IMS using VSAM local shared resource pools that IMS cannot use.