IBM System/360 System Programmer's Guide

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

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English