Creating the hardware configuration

6 Define tape drives using HCD.

Use the MVS hardware configuration definition (HCD) to define the tape drives that belong to the tape library. For an automated tape library device, specify the LIBRARY parameter as YES. For a manual tape library device, specify the MTL parameter as YES. The LIBRARY and MTL parameters are mutually exclusive.

Note: When defining the drives using HCD, device number 0000 is not supported in an automated (which includes virtual) or manual tape library environment.

The devices in an ATLDS are recognized as tape library devices as they are initialized during IPL and during IODF activation. The devices in an MTL are recognized as MTL devices only through the IODF definition.

When you define the tape drives in an ATLDS, you can optionally specify the LIBRARY-ID and LIBPORT-ID parameters. If a tape drive is then busy or unavailable at system IPL, the drive is configured based on the information provided in the optional parameters and a subsequent IODF activate should not be required. Without specification of the optional parameters, tape drives that are busy or unavailable at system IPL are not included in the library control blocks built by the system and are not eligible for allocation until the tape drives become available and an IODF ACTIVATE is issued. When you define the tape drives in an MTL, since the devices are not self-defining during IPL or IODF activation, the LIBRARY-ID and LIBPORT-ID parameters must be specified. As with an ATLDS, the LIBRARY-ID specified must match the LIBRARY-ID specified on the ISMF define panel and can be any unique five-digit hexadecimal number. The LIBPORT-ID identifies all devices attached to a specified control unit and should start with subsystem “01”. Also, note that in the MTL environment, the maximum number of subsystems supported is 32. For further information, see IPLing the system. See z/OS HCD User's Guide for additional information about using the HCD.

Note: For a Peer-to-Peer VTS Subsystem, the LIBRARY-ID specified should be the composite library ID.

Because a library may contain emulated devices, successful communication to at least one device in a subsystem must be made to determine if the devices defined through HCD are real or emulated. If the communication cannot be made during system IPL, the devices in the subsystem will not be considered eligible for allocation until successful communication has been established with the MVS VARY, ONLINE command. This will prevent the wrong device from being considered in allocation recovery.