FastSort Manual

Optimizing Sort Performance
FastSort Manual429834-003
9-5
Using Scratch Files
scratch volumes. FastSort supports up to 32 total scratch volumes: one initial volume
in the SCRATCH attribute and up to 31 SCRATCHON overflow volumes.
If the scratch file or volume specified in SCRATCH becomes full and no SCRATCHON
volumes are specified, FastSort reads the NOSCRATCHON attribute for volumes that
should not be used for overflow scratch files. You can specify up to 32
NOSCRATCHON volumes.
The SCRATCHON and NOSCRATCHON attributes are mutually exclusive. If you
specify SCRATCHON, you cannot exclude volumes from the pool with
NOSCRATCHON. Likewise, if you specify NOSCRATCHON, you cannot specify
volumes for the pool with SCRATCHON.
How Volume Characteristics Affect Selection
After checking DEFINEs for scratch volume information, FastSort creates scratch files
on volumes on your system with the following features:
The primary disk process running in the CPU where SORTPROG is running
The fewest number of currently open scratch files
The greatest amount of free disk space
FastSort automatically excludes $SYSTEM and volumes that:
Contain less than 1 MB of free disk space
Contain TMF audit trail files
Are protected by the Safeguard product
After FastSort chooses a scratch volume, it continues to create additional scratch files
on that volume until the volume is 80 percent full. When the scratch volume becomes
80 percent full, FastSort creates the next scratch file on a new volume from the pool.
Note. FastSort uses up to 100 percent of the disk space on volumes you specify in the
SCRATCH and SCRATCHON attributes. Therefore, if you explicitly specify scratch volumes,
ensure that other processes do not currently require disk space on those volumes.