The EQUALS parameter insures that the original order of equal-keyed records is preserved. These records will be in the same order in the output file as they were in the input file. NOEQUALS, the default, specifies that equal-keyed records may not be written in their original input order.
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.
When the EQUALS parameter is used with the SUM or DUPKEYS control statement, the first of the equal-keyed records is retained with the sum or DUPKEYS function value; all other records are deleted after the specified field(s) have been calculated.
EQUALS/NOEQUALS can also be specified as a PARM option on the EXEC statement. If this option is specified both on the SORT control statement and as a PARM option, the SORT specification takes precedence.
Performance is usually improved when NOEQUALS is in effect.