JCL-specified setup requirements for the IBM 3800 and 3900 Printing Subsystem cause a JFCB extension (JFCBE) to be created to reflect those specifications. Your JFCBE exists if BURST, MODIFY, CHARS, FLASH, or any copy group is coded on the DD statement. The JFCBE exit can examine or modify those specifications in the JFCBE.

Although use of the JFCBE exit is still supported, its use is not recommended.

Place the address of the routine in an exit list. The device allocated does not have to be a printer. This exit is taken during OPEN processing and is mutually exclusive with the DCB OPEN exit. If you need both the JFCBE and DCB OPEN exits, you must use the JFCBE exit to pass control to your routines. Everything that you can do in a DCB OPEN exit routine can also be done in a JFCBE exit. See DCB OPEN Exit. When you issue the SETPRT macro to a SYSOUT data set, the JFCBE is further updated from the information in the SETPRT parameter list.

When control is passed to your exit routine, the contents of register 1 will be the address of the DCB being processed.

The area pointed to by register 0 will contain a 176 byte JFCBE followed by the 4 byte FCB identification that is obtained from the JFCB. If the FCB operand was not coded on the DD statement, this FCB field will be binary zeros.

If your exit routine modifies your copy of the JFCBE, you should indicate this by turning on bit JFCBEOPN (X'80' in JFCBFLAG) in the JFCBE copy. On return to OPEN, this bit indicates if the system copy is to be updated. The 4-byte FCB identification in your area is used to update the JFCB regardless of the bit setting. Checkpoint/restart also interrogates this bit to determine which version of the JFCBE to use at restart time. If this bit is not on, the JFCBE generated by the restart JCL is used.