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7.
programs inputloutput block (lOB).
The syrooolic name for
the
lOB
is
DXIOB.
These fields (DXCCW, DXIOB) are defined by the IECDSECT
macro-instruction.
Note: There are twelve
CCW
locations
in
the
DXCCW
field.
Do not place a CCW at the location defined by DXCCW7
in your editor routine for OPEN.
Do not place a CCW
in
locations
DXCCWll or DXCCW12 in your editor routine for EOV.
To
check the retention date andlor protection fields
label you must read the data set header 1 record into
The
format
of
the nonstandard label defined by your
determines how you access the protection and retention
in
the nonstandard label.
Step 6 provides directions
the
1/0
operation.
in a standard
a
workarea.
installation
date
fields
for handling
8.
Write a message to the operator to inform him that
the
volume
is
protected and to determine if it is to be used.
9.
See step 7 above.
10.
Write
a
message to the operator to inform him that the expiration
date fer the mounted volume has not elapsed and to determine if
it
is to be used.
11.
If
the
volume is to be used, continue precessing to resolve label
or density conditions.
12.
Rewind and unload the currently mounted volume.
directions for handling the
1/0
operation.
Step
6
provides
13.
Write
a
rressage
to
the
operator
requesting dismounting of the
current volume and mounting of a new volume.
The device
name
(in
EBCDIC)
may be obtained from the UCBNAME field of the unit control
block.
14.
Step 6 provides directions for handling the
1/0
operation.
15.
Test bit 3 of the byte at
JFCB~ASK+5.
If set to one,
control
was
received as a result of a density check.
Test
bit
0 of the byte at JFCBMASK+5.
If set to one, control was
received as the result of a label check.
lSa. If control was received as the result of a label check, test bits 1
and 2 of the byte at JFCBMASK+5.
See step 5.
lSb. If control is received as the result of a density
check,
use
the
JFCBLTYP
field
in
the job file control block (JFCB) to ascertain
the type of label specified
in
the
program.
A
hexadecimal
04
indicates a nonstandard label (NSL) has been specified, a hexadeci-
mal 02
indi~ates
that a standard label has teen specified.
16.
When
correcting
a
density
check or label check condition, and a
nonstandard label (NSL) or
no
label
(NL)
is
specified
by
the
program,
you
must write some kind of record on the tape that will
be interpreted by the OPEN or EOV routines as a
nonstandard
label
or no label, i.e., it does not contain VOLl in the first four bytes
of
the record.
The easiest way to do this is to write a tapemark.
Upon return to OPEN or EOV and re-verification of
the
label,
the
specification
for
label
type and density will have been met, the
OPEN or
EOV
will
transfer
control
to
your
nonstandard
label
routines if NSL is specified or position the tape for writing if NL
has been specified.
62
The
System Control Block publication contains the format and field
descriptions for standard tape
volume
labels.
You
must
supply
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