CA Dynam for VSE User Guide

IBM Virtual Tape Facility (VTAPE) Support
If CA Dynam/T automatically creates a virtual tape, the logical unit must be
unassigned when a single file or the first file of a multi-file set is opened. If the
logical unit is preassigned, message CADT107D is issued. At that point, the
operator can either release the assignment by replying 'REL' to the CADT107D
message or cancel the job. The only time the logical unit can be preassigned is
if other than file one of a multi-file set is being opened and the previous file
used the HOLD option. See the section entitled "IBM limitation when writing to
VSAM Virtual Tapes" for more information and an example on how to create
multi-file VSAM VTAPE files.
Precautions for Virtual Tapes
The following precautions need to be taken when using virtual tapes:
• Due to a conflict between the JCLIF macro interface and POWER, do not
create or read POFFLOAD tapes using the automatic VTAPE interface.
• To prevent simultaneous use, CA Dynam/T locks virtual CUUs. An internal
method of locking is used, which requires no additional setup or options to
be set. To unlock a virtual CUU that remains locked due to cancellation or
abnormal termination of a job, use the new AR command DT READY
VCUU=cuu. The AR command DT STATUS shows NOT AVRABLE next to
any virtual CUU currently in locked status.
• To reduce the amount of I/O when searching the catalog for an eligible
virtual scratch tape, specify the VOLID parameter for data sets that are to
be written to virtual tapes. If a data set is defined with a VOLID, CA
Dynam/T performs a generic search looking only for volumes where the
first two characters match the specified VOLID. For example, if there are
no eligible virtual scratch tapes in the catalog, and no VOLID is specified,
every volume in the catalog will be accessed. However, if a VOLID is
specified, then only the volumes whose first two characters match the
VOLID will be accessed. Using the VOLID parameter limits searches only to
virtual volumes, thus reducing unnecessary catalog I/O.
• To use VSAM and FakeTape files as virtual tapes, you must define them
before they can be used by CA Dynam/T. For details about defining files to
be used as virtual tapes, see IBM or FakeTape documentation.
Example
The following is an example of how to create and read a VTAPE that will reside
in a VSAM file:
* $$ JOB JNM=VTAPE,CLASS=0,DISP=D
// JOB VTAPE CREATE VIRTUAL TAPE FILE
* STEP 1 - DEFINE VTAPE VSAM CLUSTER
// EXEC IDCAMS,SIZE=AUTO
DELETE (VTAPE.FILE) PURGE CL -
CATALOG(VSAM.USER.CATALOG)
DEFINE CLUSTER (NAME(VTAPE.FILE) -
Chapter 3: Supporting Tape File Management 3–59