4. System Access Technique Macroinstructions
4.7. TAPE VOLUME AND FILE ORGANIZATION
As was stated earlier, magnetic tape files processed by TSAT must observe certain label conventions. These were described in 4.6. Magnetic tape files must also observe conventions as to volume and file organization. The following subsections and figures describe the organization of files and volumes with respect to standard labeled, nonstandard labeled, and unlabeled files used with OS/3 tape sequential access method (SAM). Except where noted otherwise, these conventions also apply to tape files used with TSAT.
Remember that TSAT assumes only standard labeled files. TSAT bypasses user header labels, user trailer labels, and nonstandard labels. These labels are included in the following figures and descriptions only to show their relative location within the various volume organizations.
4.7.1. Standard Tape Volume Organization
A standard volume has standard labels, required tape marks, and is capable of being processed by the logical IOCS. Figures 4—i 1, 4—1 2, and 4—i 3 illustrate the reel organization for standard volumes with either an end-of-file (EOF) or end-of-volume (EOV) condition. The logical IOCS assumes that the labels appear in the order shown. A volume processed by TSAT will end in either an end-of-file or end-of-volume label group (EOF1 and EOF2 or EOV1 and EOV2) followed by two tape marks. The second tape mark signifies that no valid information follows.
User header (UHL) and user trailer (UTL) labels are optional. Tape SAM permits you to specify a special label handling routine to process these labels. If you do not specify such a routine, the optional labels are simply bypassed. However, with TSAT, you cannot specify your own label handling routine for optional labels. TSAT always bypasses these labels, and your program is not made aware of them.
On output operations, no provision is made in TSAT for the creation of additional volume labels, file header labels, or file trailer labels. If these additional labels exist on input files, TSAT bypasses them.
C
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Contents supplied by user.
SPERRY UNIVAC OS/3 SUPERVISOR MACROINSTRUCTIONS
Required arid generated by TSAT.
Generated by TSAT; user supplies content for certain fields.
Generated by user at his option. Content is at user’s option except for content of 4-byte label ID fields. User is limited to eight UHLs and eight UTLs. Bypassed by TSAT.
Figure 4—li. Reel Organization for EBCDIC Standard Labeled Tape Volumes Containing a Single File
WITH END-OF-Fl LE CONDITION WITH END-OF-VOLUME CONDITION
LEGEND:
LI
LI
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HDR2 label of file A
\
tape mark
, data blocks —
.
-. offileA
i’
tape markEOF1 label of file A
EOF2 label of file A
tape mark
HDR1 label of file B
HDR2 label of file B
tape mark
, data blocks
‘ offileB
tape mark
EOF1 label of file B
EOF2 label of file B
tape mark
II!
tape mark
LEGEND:
LI El
NOTE:
Assume that file B completes on this volume.
Figure 4—12. Reel Organization for EBCDIC Standard Labeled Tape Volume: Multifile Volume with End-of-File Condition SPERRY UNIVAC OS/3
SUPERVISOR MACROINSTRUCTIONS
4-40
VOL1 label
HDR1 label of file A
Content supplied by user.
Required and generated by TSAT.
Generated by TSAT; user supplies content for certain fields.
4-41
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REEL 2
VOL1 label
HDR1 label of file B HDR2 label of file B
\
tape mark
, data blocks
1’ offileB
tape mark
EOF2 label of file B
EOF2 label of file B
tape mark HDR1 label of file C
HDR2 label of file C
tape mark
Ii
data blocks of file C tape mark
:
EOV1 label of file C
EOV2 label of file C
tape mark
tape mark REEL 1
I
LEGEND:
Content supplied by user. Required and generated by TSAT.
Generated by TSAT; user supplies content for certain fields.
NOTE:
Assume that file C is not completed on reel 2, but carries over (like file B) onto another volume.
If file C were completed on reel 2, its EOV1 and EOV2 labels mown here would be replaced with EOF1 and EOF2 labels.
Figure 4—13. Reel Organization for EBCDIC Standard Labeled Tape Volumes: Multifile Volumes with End-of-Volume Condition
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4.7.2. Nonstandard Tape Volume Organization
A nonstandard volume is any volume that has nonstandard labels and is capable of being processed by the logical IOCS. Figures 4—14 and 4—15 illustrate the reel organization for nonstandard volumes.
Nonstandard user header and trailer labels (UHL and UTL) are optional. These may be of any format, length, or number because they are handled by the user’s label routine. When processing tapes using tape SAM, the address of the user’s label handling routine to process nonstandard labels is usually specified, in which case the tape mark following the UHL may be omitted. It is required only if label checking is to be omitted or a read-backward operation is specified. If nonstandard labels appear on an input file but are not to be checked when the file is read, the user omits specifying the address of his label
handling routine — but the tape mark must be present.
The tape mark following the data blocks is required and is written by logical IOCS, which also writes two required tape marks after the UTL, if they are present. If the optional UTL are not present, logical IOCS writes only one additional tape mark after the one following the data blocks. This second tape mark is always present when this file is the only file or the last file on the reel. It is overwritten by the next file to be written on a multifile volu me.
optional user
header labels
(
tape mark
LEG END:
Contents supplied by user.
Required and generated by TSAT; only two tape marks follow data blocks if UTLs are not present.
Generated by TSAT unless user specifies TPMARK=NO; required only if label checking is omitted or user specifies READ=BACK.
Presence, content, format, and number entirely at user’s option. Bypassed by TSAT.
Figure 4—14. Reel Organization for EBCDIC Nonstandard Volume Containing a Single File
SPERRY UNIVAC OS/3 SUPERVISOR MACROINSTRUCTIONS
LEGEND:
L1
Content supplied by user.optional user header labels tape mark
data blocks
1—
offileA
tape mark optional user
trailer labels tape mark optional user header labels tape mark
data blocks of file B
tape mark optional user trailer labels
tape mark
tape mark
Iii
E,
Required and generated by TSAT; only two tape marks follow data blocks of last file on volume if UTLs are not present.LI
Generated by TSAT unless user specifies TPMARKNO; required only if label checking is omitted or user specifies READBACK.Presence, content, format, and number entirely at user’s option. Bypassed by TSAT.
Always present; written by TSAT
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Figure 4—15. Reel Organization for EBCD/C Nonstandard Muftifile Volume
4.7.3. Unlabeled Tape Volume Organization
An unlabeled volume is any volume that has no labels and is capable of being processed by the logical IOCS. The user specifies FILABL=NO, or omits this parameter in the TCA macroinstruction, to indicate an unlabeled volume or file. A tape mark is expected or written by logical IOCS preceding the data blocks unless the user has specified TPMARK=NO in the TCA macroinstruction.
Figure 4—16 illustrates the reel organization for unlabeled volumes. The tape mark following the data blocks is required on both single-file and multifile volumes and is supplied by TSAT on output operations. A second tape mark is always written by TSAT following the last or only file on each volume and is overwritten by the next file to be written on a multifile volume.
data blocks /
L’
tape mark\\\\\\
tape mark
Generated by TSAT unless READ=’BACK.
tape mark
, data blocks
of file A
tape mark
h
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tape mark
SINGLE-FILE VOLUME
LEGEND:
L1
Content supplied by user.Required and generated by
LI
MULTIFILE VOLUME
TSAT; two tape marks follow data blocks of last file on volume.
user specifies TPMARKNO; required only when user specifies
Figure 4—16. Reel Organization for Unlabeled EBCDIC Volumes
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