Displaying Messages on Cartridge Magnetic Tape Subsystems (MSGDISP macro)

This information covers using the MSGDISP macro to display messages on magnetic tape devices that have displays. With MSGDISP, you can specify the message to be displayed and how to display it (for example, steady or flashing). The standard, executes, and list forms of the macro are described here. The six main parameters of the macro and their functions are:

Value	Meaning
MOUNT	Displays an 'M' in position 1 of the display area during a mount request until a volume is loaded and made ready. The 'M' is followed by the volume serial number and label type.
VERIFY	Shows that a volume has been accepted by displaying its serial number and label type in positions 2 through 8.
RDY	Displays text in positions 2 through 7 while a data set is open.
DEMOUNT	Places a volume disposition indicator in position 1 of the display until a volume is demounted.
RESET	Clears the display area.
GEN	Provides the full range of display options, including the option to alternate two messages.

All except the RDY parameter require that the caller be in supervisor state, have a storage protect key of 0 through 7, or be authorized by the authorized program facility.

You can issue the MSGDISP macro in 24- or 31-bit addressing mode. When you use 31-bit addressing mode, all addresses must be valid 31-bit addresses.

The MSGDISP macro generates a parameter list as input to the message display service routine. You can code an installation exit routine named IGXMSGEX,which gains control when MSGDISP is processing MOUNT, DEMOUNT, VERIFY, or GEN requests. The exit can change the message text displayed (two 8-byte strings) and 1 bit of the format control byte. See the publication z/OS DFSMS Installation Exits z/OS DFSMS Installation Exits z/OS DFSMS Installation Exits for details.