READ

The assembler calls the exit with a request type of 3 (READ) when the exit is supplying the library records, and after a successful FIND request. For copy members, the assembler calls the exit until the exit indicates the end-of-file. For macro definitions, the assembler calls the exit until it receives a MEND statement, or the exit indicates the end-of-file.

The exit sets the return code in the Exit Parameter List to one of these values:

0: The exit is supplying a record. The record must be placed in the area pointed to by the buffer pointer field. The record area is 80 characters in length.
The user exit should maintain the absolute record number and the relative record number. These fields are set to zero before the OPEN request. The assembler uses the relative record number in diagnostic messages when you specify the FLAG(RECORD) assembler option. If you specify the ADATA assembler option, the assembler includes both fields in the associated data file Source Analysis record.

Note: A reason code of 8 requests redrive of the exit.
16: Indicates to the assembler that there are no more records. This is equivalent to end-of-file processing for input members.
Note: A reason code of 8 requests redrive of the exit.