Non-synchronous storage subsystems

Allocation of work data sets on devices attached to non-synchronous storage subsystems can affect the performance of certain DFSORT applications. Whether or not a particular application is affected depends on many factors, the most critical of which is the ratio of input file size to available storage.

In general, to maximize performance, DFSORT needs the following:

Accurate knowledge of the size of the file being sorted
In most cases, DFSORT is able to calculate the file size accurately. However, for applications that sort many input tapes that are not managed by DFSMSrmm or a tape management system that uses ICETPEX (especially compacted input tapes) or that use E15 exits that add or delete records, we recommend that you specify the file size using the FILSZ or SIZE parameter.
Adequate storage relative to the size of the file being sorted
Table 1 shows the minimum recommended storage to provide DFSORT based on various input file sizes.

Table 1. Minimum Storage Required for Various File Sizes
Minimum Storage Required for Various File SizesInput file size	Minimum storage
Less than 200MB	4MB
200MB to 500MB	8MB
500MB to 1GB	16MB
More than 1GB	16-32MB