Guardian Programmer's Guide

Communicating With Magnetic Tape
Guardian Programmer’s Guide — 421922-014
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Working With Standard Labeled Tapes
Working With Standard Labeled Tapes
The operating system provides support for magnetic tapes written with standard ANSI
or IBM labels. The labeling mechanism allows for easy transfer of information between
systems from different vendors using magnetic tape.
Both the ANSI and IBM standards use labels to describe tape volumes, files, and file
sections. Here, a tape volume is a complete tape reel; a file is a file of information
written to the tape; for large files, a file section identifies the part of a file that resides
on a given tape volume. The concept of a file section therefore makes it possible to
have tape files that occupy more than one tape reel.
For full details of the ANSII standard see the ANSI X31.27-1987 standard as described
in “File Structure and Labeling of Magnetic Tapes for Information Interchange”
published by the American National Standards Institute. For the layout of the IBM and
ANSI label structures, see the Guide to Common System Operation Tasks.
Enabling Labeled Tape Processing
To enable labeled tape processing, your system must be set up as follows:
•
Tape-label processing must be turned on at system-generation time. Refer to the
System Generation Manual for Disks and Tapes for details.
•
The labeled tape server process $ZSVR must be running. This process is typically
started during cold load.
HP sites can create their own labeled tapes, or they can work with tapes written at any
site with any equipment so long as the tape contains standard ANSI or IBM labels.
Creating Labeled Tapes
Labeled tapes created at a HP site must first be initialized by the MEDIACOM utility or
the TAPECOM utility, which put volume labels on the tape and an indication that this is
a scratch tape. Refer to the DSM/TC Operator Interface (MEDIACOM) for details on
the MEDIACOM utility; refer to the Guardian Disk and Tape Utilities Reference Manual
for details on the TAPECOM utility.
Checking for Labeled Tape Support
You can check whether labeled tape support is turned on by calling the
LABELEDTAPESUPPORT procedure:
RETURNED^VALUE := LABELEDTAPESUPPORT;
IF RETURNED^VALUE = 0 THEN CALL PROCESS_STOP_
ELSE ....
!continue labeled tape processing
The value returned by the LABELEDTAPESUPPORT procedure is 0 if tape-label
processing is not turned on or 1 if tape-label processing is turned on.