HP NonStop G-Series - Manual (Page 62)

DSM/TC Tape Processing
DSM/Tape Catalog User’s Guide — 520233-008
3 - 10
DSM/TC Interaction With $ZSVR
replacement tapes during audit dump restoration if multiple parallel or serial audit
dumps were performed, use the MEDIACOM ALTER TAPEMOUNT request.
DSM/TC Interaction With $ZSVR
To use MEDIACOM commands effectively, you should understand how the NonStop
Kernel tape server process, $ZSVR, and DSM/TC interact with each other.
How Users Request Labeled Tapes
As a user of labeled tapes (a requestor), you must first create a TAPECATALOG
DEFINE for each tape file to be accessed. The DEFINE contains attributes describing
the tape file, such as the file ID, and the operation, such as input or output. If the
application program you are using is coded to expect certain DEFINE names, you must
give those names to the DEFINEs you create.
After creating the DEFINEs, you can run your application program, specifying the
DEFINE names in the run command.
How $ZSVR Manages Tape Requests
When an application opens a file described by a DEFINE:
1. An open request is sent to $ZSVR through the file system. The request contains
the information from the DEFINE.
2. $ZSVR must know which tape can satisfy the request. It makes one of these
requests of DSM/TC:

Find the tape that contains the cataloged tape file ID named in the DEFINE.

Verify that the tape named in the DEFINE contains the cataloged tape file ID in
the DEFINE.

Select an available scratch tape from the pool specified in the DEFINE.
Otherwise it uses the currently loaded tape and appends another backup job to
the same tape media if the tape is defined as appendable.

Verify that the scratch tape named in the DEFINE is a cataloged scratch tape.
3. $ZSVR uses Automatic Volume Recognition (AVR) to find the drive on which the
tape approved by DSM/TC is mounted.

If the tape is already mounted, meaning the operator put the tape on a drive
before a mount message was generated for it, $ZSVR immediately connects
the tape drive to the application so it can use the tape.

If the tape is not mounted:
a. $ZSVR checks if another mounted tape can satisfy the request. If so,
$ZSVR proceeds to Step d.