There are four programming PARMs that may have a significant effect on sort performance: CMP, EQUALS, STOPAFT, and SKIPREC.
The CMP PARM specifies the kind of compare operation to be used for sort/merge control fields up to 16 bytes long, bearing the format code PD or ZD. When CMP=CPD, the default, is used, ZD fields are PACK’ed and then compared. Invalid PD data may cause a system 0C7 abend and program termination. The integrity of fields labelled “ZD” is only guaranteed when they contain valid ZD data. The delivered default of the VLTEST PARM supports CMP=CPD, as do certain other VLTEST PARM values. Whenever possible, set CMP= CPD for better sort performance.
The alternative, CMP=CLC, is a more costly option--it forces the sort to extract potentially invalid PD and ZD fields and do a certain amount of data manipulation to obtain valid sign comparisons.
The EQUALS PARM instructs the sort/merge to preserve the order of equal-keyed records. EQUALS will have a slight but generally significant impact on sort performance. By making EQUALS available on an individual sort basis, MFX makes this programming option available where it is needed, without imposing it on the installation’s more routine jobs. For sort efficiency, use EQUALS only where the preservation of the input order of equal-keyed records is important.
Users interested in sort performance should specify the STOPAFT PARM in test runs of the sort. With STOPAFT=n, only the first n records of the input file will be sorted. By reducing the number of records to be processed, STOPAFT improves sort performance. If additional tests are necessary, the SKIPREC PARM can be used together with STOPAFT to select a different subset of the SORTIN data set.