Reduce 4GB-limited space allocations (VSAM_4GB_EXT_REDUCE)

The VSAM_4GB_EXT_REDUCE function will adjust allocations for 4GB-limited, non-extended addressability data sets such that the allocation will not cause that allocation to exceed the 4GB limit. For secondary allocations the extent size will be adjusted to the nearest control area size multiple of allocations units (cylinders or tracks) that is at or below the 4GB limit. For initial primary allocations the error indicating that the primary allocation amount exceeds the 4GB limit for a data set will be detected and normal primary allocation reduction processing will occur.

Syntax

Read syntax diagramSkip visual syntax diagramVSAM_4GB_EXT_REDUCE=DISABLEENABLE

VSAM_4GB_EXT_REDUCE=ENABLE|DISABLE

Operands

ENABLE
Reduce the allocation to prevent the allocation from exceeding 4GB.
DISABLE
Do not reduce the allocation to prevent the allocation from exceeding 4GB.

Default

DISABLE

Environments

ALLOCATE, EXTEND

Usage and processing considerations

This function is supported for all VSAM data set record organizations for all data sets which do not specify the Extended Addressability attribute in the data set’s associated SMS Data Class. For those data sets for which it is not supported the function is ignored.

For initial primary allocations for supported data sets the error indicating that the primary allocation exceeds the 4GB limit for a data set will be detected and normal primary allocation reduction processing will occur. The restriction that initial primary allocations that specify Guaranteed Space will be bypassed for processing by Advanced Allocation Management still applies.

For supported data sets for secondary allocations and the primary allocation on a candidate volume the extent size will be adjusted to the nearest control area size multiple of allocation units (cylinders or tracks) that is at or below the 4GB limit.

This function will be performed for supported data sets for any extent added or adjusted in size by any Advanced Allocation Management function as well as for any secondary allocation extent which is intercepted by Advanced Allocation Management but not otherwise handled.

Related keywords

VSAM_4GB_WARN_MSG, VSAM_4GB_WARN_MSG_PCT

Example

In the following example, VSAM_4GB_EXT_REDUCE=ENABLE specifies that the VSAM_4GB_EXT_REDUCE function is enabled.

* RULE DEFINITIONS
*
DEFAULTS
 .
 .
EXCLUDE JOBNAME=ABCJOB1    * Item to exclude from processing
INCLUDE JOBNAME=ABCJOB*    * Item to include in processing
VSAM_4GB_EXT_REDUCE=ENABLE * Enable 4GB extent reduction

The EXCLUDE keyword specifies the selection criteria that are to be excluded from Advanced Allocation Management processing. In the example, jobs that have a job name of ABCJOB1 are excluded from Advanced Allocation Management processing. If Advanced Allocation Management encounters an extent allocation for a data set in a job that has a job name of ABCJOB1 and that allocation would cause the size of the associated data set to exceed 4GB in size, Advanced Allocation Management would not reduce the size of that extent.

However, if Advanced Allocation Management encounters a job that has a job name that starts with ABCJOB other than ABCJOB1, it would reduce the size of extents that would cause the size of the data set to exceed 4GB as directed by the VSAM_4GB_EXT_REDUCE keyword because the INCLUDE statement specifies that jobs with job names that begin with ABCJOB are to be included in Advanced Allocation Management processing.