Device management for FDDRL

In FDDRL there are numerous links to Nucleus Device Management (NDM), the BS2000 device management facility.

• Data volumes are allocated the usage mode “SPECIAL“. This is shown by USE=SPECIAL in the mount requests (NKVD013, NKVT013) and in the output of the commands /SHOW-DISK-STATUS and /SHOW-TAPE-STATUS.

• FDDRL allocates data volumes (including private disks) as “task-exclusive“. For this reason they must be free before they are allocated (PHASE=ONLINE). Also, they cannot be requested by other tasks while they are being used by FDDRL.

• Disks are allocated as “system-exclusive” (NKVD013) with SYS-ALLOC=EXCL. The system ID of this system’s home pubset is entered in the system allocation log of the standard volume label so that simultaneous use of the disk by other systems is prevented. The type of allocation is shown in /SHOW-DEVICE-STATUS and /SHOW-DISK-STATUS (VOL-A=EXCL).

• When processing private disks with FDDRL you should note the following: if the disk was mounted using /SET-DISK-PARAMETER or /SET-DISK-DEFAULTS with the attribute ASSIGN-TIME=*OPERATOR, the private disk is occupied by DMS as soon as it is switched online. In this case the disk must be released using the command /SET-DISK-PARAMETER VOL=<vsn>,ASSIGN-TIME=*USER.

• If FDDRL processing is performed under subtasks, disk and tape devices may not be reserved under the main task with the /SECURE-RESOURCE-ALLOCATION command since this reservation cannot be passed on to the subtasks. Devices reserved in this way would be blocked for the subtasks. Tape devices which are required are reserved by the FDDRL subtask itself. Here the subtask waits for the period specified in the FDDRL parameter SECURE-WAIT-TIME.

• In the case of FDDRL tapes, a VOLUME-MOVE (/CHANGE-TAPE-MOUNT) is possible in spite of the SPECIAL allocation so that hardware errors can be avoided.