Pg. of GC20-1819-2 Rev March 30, 1979 by Supp. sn23-9024-1 for 5748-XX8 You define a standard label tape with the DTFMT parameter FILABL=STt. You also must supply a LABELDEF command to specify label descripticn
information. This command replaces the DOS/VSE TLBL card and is
required for standard label processing under CMS/DOS. The LABELDEF command is discussed in detail in the "LABELDEF Command" section later
in this publication.
In order to connect the LABELDEF command for a file with the DTFMT for the same file, you must use the same name to label your DTFMT as you
use for a filename in your LABELDEF command. If you code a DTFMT macro
in your program as: MTl DTFMT ••• FILABL=STD you must then supply the following type of LABELtEF command:
labeldef mtl fid yourfile fseg ••• You can put any description parameters you want on your LAEELDEF
command but the filename for it must be mt1 if you coded MTl as the
label on the DTFMT.
After you have set up your DTFMT and LABELDEF, you execute your CMS/DOS program. HDR1 labels are checked or written when an OPEN macro
is issued. EOF1 labels are checked or written when a CLOSE macro is
issued. A VOLl label volume serial number is checked only if the tape
is positioned at load point when the label processing tegins and if you
have specified a VOLID parameter on a LABELDEF statement for the file.
Note, if NOREWIND is not specified in the DTFMT macro for the file. the
tape is rewound so it is positioned at load point for label processing.
If you want to process user standard labels as well as standard
labels in CMS/DOS, you specify FILABL=STD and also supply a LABADtR parameter in the DTFMT for the file. Control is then transferred to
your label processing routines after standard labels are processed. The
linkage to user standard label routines is exactly the same as in DOS/VSE. There are minor differences in the way tapes are processed by eMS/DOS and the way they are processed by DOS/VSE. These differences are: I The tape error messages are CMS error messages and not DOS/VSE error I aessages. In some cases DOS/VSH allows the system operator to reply NEWTAP to an error Bessage. The system then waits for the operator
to mount a new tape and continues processing with this new tape. Such a reply is never possible under CMS/DOS. In CMS/DOS, you
usually can reply IGNORE to ignore a tape label error condition or
CANCEL to cancel a job. NEW TAP is never allowed. In a few cases, CMS/DOS allows an IGNORE reply where DOS/VSE does not. You must specify CLOSE to process all trailer labels. No automatic CLOSE occurs at end of data or after reading a tape mark. If an
input tape is positioned at an EOF1 or HOV1 record when CLOSH is
issued, the label is processed. If a tape file is closed before all
data records are read, the trailer label is not processed. Output 122.8 IBM VM/370 CMS User's Guide
Pg. of GC20-1819-2 Rev March 30, 1979 by SUppa SD23-9024-1 for 5748-IX8 tapes have EOF records written only at CLOSE time. For nonstandard
labelled tapes, your own routines do not receive control on input
when a tape mark is read. You must issue a CLOSE macro in your EOFADDR routine in order to have the trailer labels processed. Certain fields in HDR1 and EOF1 labels default to values different
from those in DOS/VSE. For example, the default volume serial number
written in a HDR1 label is CMS001 and not the actual volume serial
number (volid) in the VOL1 label already on the tape. The default
file sequence and volume sequence numbers are always one even wben
the file is not the first file on the tape. You should read tbe
section on the LABELDEF command in this publication to learn what the
default values are in CMS/DOS. You also can read the IBM publication to find what the default values are for DOS/VSE. If you do not like the default values, you can always specify the
exact values you want in label fields in a LAEELDEF command. Expiration date specification is always done in absolute form rather
than by retention period. You must always use the form yyddd where
yy is the year (0-99) and the ddd the day (0-366). CMS does not
handle expiration dates specified by retention periods. VOL1 labels written in the wrong density are not rewritten
automatically by CMS/DOS as they are by DOS/VSE. Blank tares should not be used for tape files specified as FILABL=STD in they will run off the reel. Use eM5 TAPE command to
write a VOL1 label or a tape mark on a blank tape before using it fcr
a STD file. I Not all tape movement and label checking that occurs in DOS/VSE I occurs under CMS. For example, when opening an output r1ie, a DOS/VSE system expects the tape to be positioned at a HDR1 label or a
tape Marko It then backspaces the tape to read the last EOF1 label
on the tape. If it does not find the label it expects, it issues an
error message. This check is not performed by CMS/DOS. If the tape
is not positioned at a HDR1 label or a tape mark when output open
processing begins, error message 422 is issued. After an EOV1 label is written (see "End-of-Tape/End-of-Volume Processing" later in this publication), the tape is always rewound
and unloaded under DOS/VSE lets a DTFMT parameter control
whether or not the tape is rewound. User label processing routines do not receive control when an I/O error occurs under CMS/DOS. Control is not passed to user standard label routines in CMS/DOS when EOT has been sensed on output and an EOV1 label has been written by
the system routines. Work tapes are not checked for an expiration date when they contain
standard labels under CMS/DOS. If a tape is to be opened as a work
tape, eMS/DOS tests to see if it contains a VOL1 latel. If it dces,
a dummy HDR1 label and a tape mark are immediately written on the
tape after the VOL1 label. If the tape does not contain a VOL1 label, a tape mark is written at the beginning of the tape. DOS/VSE checks expiration dates on previously labelled tapes used as work
tapes and gives the operator a chance to reject the tapes if the
expiraticn date has not expired. Section 7. Using Real Printers, Punches, Readers, and Tapes 122.9
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