The SQUASH command tries to move allocated areas on disk so as to reduce fragmented disk allocation and to create larger available areas.
Syntax
Explanation
SQUASH <family name>
Starts the system process SQUASH/<family name>, which tries to compact the allocated space on the family. If the family has more than one member, the process compacts each online member. If a pack is mirrored, changes made to it are made also to the other members of its mirrored set.
SQUASH <family name> (<family index>)
Only the family member specified by <family index> is compacted.
Examples
This example starts a process to compact the allocated space on the family named DMSIITEST.
SQUASH DMSIITEST
Considerations for Use
The SQUASH procedure does not move areas of files from one pack in a family to another pack in the family.
When the SQUASH command is used, the system attempts to consolidate available disk areas by moving from a specific area of the disk all disk areas that are in use. The system selects the starting address of the area to be cleared based on the size of the rows, the status, and the kind of files located in the area, and the amount of available space already available in that area. The size of this area is 95 percent of the total available space on the disk. Rows that are in use within this area are not moved if they are larger than any contiguous available space elsewhere on the disk. Therefore, you should consider the following when using the SQUASH command:
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If the fragmentation of available space is severe, a SQUASH command might not be able to move any areas, or might result in making the largest available area smaller.
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A SQUASH operation is most successful if it is done before the available space is severely fragmented. As a preventive measure for disks that are prone to fragmentation, it is recommended that a SQUASH operation be performed routinely during non-peak processing hours.
The SQUASH command can specify a family name that is in use. During the execution of the SQUASH process, the available space on the disk decreases progressively until the squash area is released at the end of the process. If a program requires space that is not available on disk, it can go into a waiting state. This condition is indicated in the waiting entry as SECTORS REQUIRED ON <family name>.
Only one RES (Reserve) or SQUASH command can be active on a given disk family at any given time. You cannot enter a SQUASH command while a RES or an XD (Bad Disk) command is active on the same family, and you cannot enter a RES command while a SQUASH command is active on the same family.
