Increased parallel input processing (up to four SORTPARn DDs) increases the elapsed time benefit. However, for optimal PARASORT performance, MFX must be able to read each SORTPARn input DD simultaneously with no channel contention.
Generally, the normal allocation of tape drives will not ensure sufficient channel path availability, particularly for a 4-way PARASORT (four SORTPARn DD statements). Therefore, you may need to create special esoteric unit names for PARASORT. Assigning certain groups of drives to each esoteric unit name used in the PARASORT JCL will in most cases ensure the required channel separation.
The procedure for creating PARASORT esoteric unit names consists of three steps:
- Run the SYNCLIST report program to create a report of available tape drives and potential esoteric unit names.
- Implement the esoteric unit names in the report.
- Distribute the esoteric unit name table to developers of PARASORT applications.
The following three sections describe the steps in detail.