The EQUALS option affects the order in which equal-keyed records are processed. Equal-keyed records are records with identical values in all key fields.
If you specify NOEQUALS, the output sequence of the records within a set of equal-keyed records will be unpredictable. NOEQUALS is the default.
If you specify EQUALS, the records within a set of equal-keyed records will be released in the same order, relative to each other, in which they entered the sort or merge.
Depending on your z/OS environment, preserving the order of equal-keyed records can add overhead to sort and merge processing. However, in most environments you can significantly reduce the amount of EQUALS processing overhead by continuing MFX performance improvements.
Because preserving the order of equal-keyed records adds overhead to sort and merge processing, you should only specify EQUALS when necessary.
If a single file is sorted and the EQUALS option has been chosen, the order of the records with equal key fields will be the same in the output file as in the input file.
If EQUALS is chosen for a sort or a merge and there is more than one input file, equal-keyed records from individual input files will appear in contiguous sets in the output file. These sets will be in the order in which their respective input files were defined to the application.
If EQUALS is in effect in an application with SORTMInn data sets, the order of equal-keyed records within each SORTMInn file will be preserved. In addition, equal-keyed records from the lowest-numbered SORTMInn file will be written before those from the second SORTMInn file, and so on.
If you are using a SUM or DUPKEYS control statement with MFX during a particular application and you wish to guarantee that the record preserved is the first record originally released for processing, you can use the EQUALS parameter at execution to override the default set at installation.