IBM System/360 System Programmer's Guide

SECTION 2: VOLUME LABEL AND DUAL-DENSITY TAPE DEVICE EDITOR ROUTINES
When writing data sets on magnetic tape (OUTPUT or OUTIN specified in
the OPEN macro-instruction) conflicts may be detected between:
1. The label type specified by the program and the label type on the
currently mounted volume.
2. The recording density specified by the program, and the density at
which a dual-density tape device is set to record.
These volume label and density conflicts are detected by the OPEN or
EOV control program routines during label verification procedures. IBM
supplies editor routines that function when these conflicts are
detected, resolving the conflicts by requesting dismounting of the
currently mounted tape volume and the mounting of a new tape volume
whose label and/or density conform to the program specifications. The
editor routines you write replace the IBM supplied routines, and can be
designed to resolve the label and density conflicts without operator
intervention (i.e., tape handling).
Your editor routines can resolye label and density conflicts by
writing labels, "cancelling labels," and by performing write operations
to set the desired density on a dual-density tape device. Or, your
editor routines can reset system control blocks (in effect, change the
program specifications) to agree with the label type and/or density of
the currently mounted volume. Or, your installation may desire a
combination of these actions, including dismounting under certain
conditions. All these possible actions way be included in your editor
routines.
You may replace the standard IBM editor routine associated with the
OPEN routine; the standard IBM editor routine associated with the EOV
routine, or both.
The balance of this section provides you with the information
necessary to write editor routines; progra~ming conventions, entry
conditions, a suggested logic for your OPEN and/or EOV editor routines,
and how to insert your routines in the control program.
PROGRAMMING CONVENTIONS
Your editor routines must conform to the same general programming
conventions as the nonstandard label processing routines discussed in
section I of this chapter (see section I - Programming Conventions) in
so far as size, design, register usage, entry points, and work areas are
concerned.
You must name the first (or only) module of your routines as follows:
OMODVOL1
EMODVOL1
the editor routine associated with OPEN
the editor routine associated with EOV
If your editor routines consist of more than one load module, nawes
for the additional modules must begin with the prefix OMODVOL for the
OPEN routine. EMODVOL for the EOV routine. Transfer between the modules
must be by name.
As discussed in Section I of this chapter, you must use EXCP
prograrrming to perform the needed input/output operations.
Label Processing Routines 55

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English