AVS_ALGORITHM

Syntax

AVS_ALGORITHM=BESTFIT|FIRST|LARGESTSINGLE|MOSTFREESPACE |PERFORMANCE

Operands

BESTFIT

Select the volume (or volumes) with a single extent in which the requested amount is closest to the requested primary allocation quantity without being less than the requested primary allocation quantity.

FIRST

Select the first volume (or volumes) that have enough total freespace to satisfy the requested allocation amount.

Note: The allocation amount might not be able to be satisfied because the freespace that is needed might be spread across more than five extents, which is the normal limit within allocation for satisfying a space request. Therefore, you might need to specify PRIM_REDUCE to help make the allocation successful.

LARGESTSINGLE

Select the volume (or volumes) with the largest single free extent.

Note: Advanced Allocation Management selects the volume with the largest single extent. This does not mean that the volume has enough space to satisfy the requested amount, it indicates that it is the volume with the largest single extent. Therefore, you might need to use the PRIM_REDUCE function to handle those situations where the selected volume does not have adequate space available.

MOSTFREESPACE

Select the volume with the most available freespace. The most available freespace is defined as the total number of free cylinders or tracks, on the volume, depending upon the allocation unit that is used. If you specify cylinder allocation, the total number of free cylinders is considered. Otherwise, the total number of free tracks is considered.

PERFORMANCE

Select the volume with the lowest fragmentation index, giving preference to volumes that have enough available freespace to satisfy the allocation request.

Usage and processing considerations

• If more than one volume is to be selected as specified in the volume count, Advanced Allocation Management chooses multiple volumes, starting with the best candidate as defined by the algorithm that is chosen, down to the least eligible candidate.
• For the BESTFIT and FIRST algorithm, as the size of the extent must at least contain the requested primary quantity, it is possible that Advanced Allocation Management might not find enough volumes that are based on the algorithm to satisfy the volume count that is specified. In this case, the remaining volumes, up to the volume count specified, are chosen using the MOSTFREESPACE algorithm.
• When Advanced Allocation Management chooses initial volumes using AVS, the allocation request is converted to a specific volume request.

Tips:

The following suggestions are dependent upon sizes and patterns of data set creation and deletion and your results might vary.

• To fill volumes in sequence, leaving other volumes mostly empty for large allocations, consider specifying FIRST or BESTFIT. Specifying FIRST tends to fill the volumes in order of specification in the various volume groups.
• To distribute allocations evenly among all volumes in a volume group, consider specifying MOSTFREESPACE and LARGESTSINGLE. In most cases, specifying MOSTFREESPACE followed by LARGESTSINGLE tends to evenly distribute the allocations across the volumes that are listed in the volume groups.

Default

LARGESTSINGLE

Environments

ALLOCATE

Related keywords

AVS, AVS_MOUNT_USAGE, AVS_UNIT, AVS_VGRP, AVS_VGRP_SEARCH, and AVS_VSER.