FastSort Manual

Sorting in Parallel
FastSort Manual—429834-003
6-9
Specifying the Size of the Extended Memory
Segment
Specifying the Size of the Extended Memory Segment
If you do not specify an extended segment size for a subsort process, FastSort tries to
use enough memory for the subsort to make only one merge pass. In the automatic
configuration, the segment size is at most 50 percent of the processor’s physical
memory not locked down by the operating system.
FastSort computes the actual size of the segment as follows, using the segment size
for a serial sort run (s) and the number of subsort processes (n):
This is the default extended segment size for a subsort process. To specify a different
extended segment size, use one of these parameters:

The SEGMENT parameter of the SUBSORT command

The process-start parameter of the SORTMERGESTART procedure

The SEGMENT attribute of a SUBSORT DEFINE
If you do not explicitly specify the segment size for a subsort process, the subsort
process uses the same segment size as the distributor-collector process.
To specify the maximum segment size for all subsort processes, you can use:

The MINTIME or MINSPACE parameter of the RUN command

The process-start parameter of the SORTMERGESTART procedure

The MODE attribute of a SORT DEFINE
Specifying a Location for the Swap File
The default location for the swap file in an extended memory segment is the same disk
volume where the scratch file is located if the scratch file is local. For remote scratch
files, the default is the volume where the program file is running. You can specify a
volume for the swap file by using one of these parameters:

The SWAP parameter of the SUBSORT command

The process-start parameter of the SORTMERGESTART procedure

The SWAP attribute of a SUBSORT DEFINE
Swapping, or paging, occurs only when the extended memory segment is larger than
the available physical memory or when there is competition from other processes. To
avoid swapping, specify less extended memory for the subsort process or move the
process to a processor with more physical memory available or a lighter load
s
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n
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