The assembler calls the exit with a request type of 4 (WRITE) when the exit is writing the object records. The buffer pointer field points to the object record, and the buffer length contains the length of the record.

z/VM and z/OS

The record length is always 80 bytes when you specify the NOGOFF assembler option. If you specify the GOFF assembler option, the record length is 80 bytes for fixed-length output or up to 8212 bytes for variable-length output. The record length for variable-length records does not include the 4-byte length of the record descriptor word (RDW), and the buffer pointer field points at the object data, not the RDW.

z/VSE

The record length is always 80 bytes.

The user exit should maintain the absolute record number and the relative record number. These fields are set to zero before the OPEN request.