DSM/Tape Catalog User's Guide

DSM/TC Tape Processing
DSM/Tape Catalog User’s Guide — 520233-008
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Using VOLUME (Tape Name)
10> & USE OUT,&
10> & POOL TEST_MISC,&
10> & FILEID SALES_REPORT_LOCAL
When your application opens the output file, $ZSVR takes the usual steps to obtain the
name of a scratch tape from DSM/TC. $ZSVR receives the name TAP15 and issues a
mount message for it:
... $ZSVR : 0063 *MC* MOUNT TAP15 WITH RING
Instead of mounting TAP15, the operator mounts tape TAP20 from a stack of scratch
tapes belonging to the TEST_MISC pool because TAP20 is on the top of the stack.
$ZSVR discovers that TAP20 is mounted and does not match any current mount
messages. $ZSVR checks with DSM/TC to verify that this tape is cataloged in
TEST_MISC as scratch. DSM/TC verifies TAP20, so $ZSVR connects it to the
application to complete the request.
During this process, the status of the volume catalog entries for TAP15 and TAP20 are
changed as the various events take place. By the time the tape request is complete,
TAP15 has passed from scratch to selected, and back to scratch (once more available
as a scratch tape). On the other hand, TAP20 has passed from scratch to in use,
reflecting that the application is writing data to it.
Using VOLUME (Tape Name)
When one or more tape names are specified as part of the VOLUME attribute, you
want to have certain tapes used for an output tape file. In the most straightforward
case, these actions take place for each tape named by VOLUME:
1. $ZSVR asks DSM/TC to verify the tape name as a cataloged scratch tape.
2. DSM/TC verifies the tape and reserves it.
3. $ZSVR issues a mount message for the t
ape and then connects the tape drive to
the application after it determines which drive the tape is on.
If all the tapes named by the VOLUME attribute are cataloged as scratch when
DSM/TC verifies them, the tape file is written to the tape volume you wanted. However,
when a named tape fails the verification step, DSM/TC automatically substitutes the
next scratch tape in the VOLUME list for it. DSM/TC also keeps supplying scratch tape
names if you did not name enough tapes with VOLUME to contain the tape file or files.
This flexibility lets an application continue processing without interruption.
The substitution process is:
1. DSM/TC discovers the tape’s entry does not have a scratch status. If the tape is
the only one or the last one in the VOLUME list, DSM/TC chooses a tape from the
Note. If you are familiar with TAPECOM commands, you recognize that the previous tape-
switching example for TAP15 and TAP20 illustrates the function of the USETAPE command for
TMF scratch tapes. This function is built into DSM/TC and applies to scratch tapes requested
with VOLUME SCRATCH by any application using a TAPECATALOG DEFINE, not just by
TMF.