Use of the parameter UEPFSHIP

UEPFSHIP contains the address of a 16-byte area. This area consists of 4 characters, followed by 3 fullwords.

If the first byte contains 'Y', this request has been function shipped to this region. In this case, if your exit program wants to bypass file control (by setting a return code of UERCBYP), it must set the 3 fullwords as follows:
Fullword 1
The length of the buffer area
Fullword 2
The length of the record
Fullword 3
The length of the modified RIDFLD.

Doing this ensures that the data and RIDFLD are correctly shipped back.