The STOPAFT=n parameter specifies the number of records to be copied. These will be the first n records after INCLUDE/OMIT and SKIPREC processing, if specified, have completed.
The STOPAFT parameter should only be specified for a MERGE FIELDS=COPY operation. STOPAFT will be ignored when doing a merge of multiple SORTINnn data sets.
If STOPAFT is specified as a PARM option as well as on the MERGE control statement, the PARM specification takes precedence.