Systems Reference Library

Systems  Reference  Library
File No. GENL 20
Form C28-8142
Systems Reference Library
IBM Standard Tape Label
This publication describes the format of the IBM
standard tape label and the conventions for its use.
The publication for any program that implements the
standard label will indicate that the program does so.
The standard label was designed for use on tapes for
the following tape units:
1.
IBM 729 II, III, IV, V, and VI Magnetic Tape Units
2. IBM 7330 Magnetic Tape Units
3. IBM 7340 Hypertape Drives
The IBM standard tape label contains 120 alphameric
positions and serves as both a header label and a trailer
label. There are two types of trailer labels:
end-of-file (EOF) trailer labels and end-of-reel (EOR)
trailer labels.
iJ
19F3. by Internati~nal Business Machines Corporation
Copies of this and other IBM publications can be obtained through IBM Branch
Offices. Address comments concerning the contents of this publication to
Programming Systems Publications, IBM Corporation, P. o. Box 390, Poughkeepsie, N. Y.
TAPE FORMATS AND LABELING
RECORDING METHOD
Figure 1 illustrates the use of the standard label in
the basic tape data formats and on data tapes containing physical tape records (blocks) of checkpoint data.
The various tape formats are described below.
All header and trailer labels must be written in
binary coded decimal (even parity) regardless of the
recording method used for the data in the body of the
file.
Single-Reel File
MODE (7340)LABELS
A single-reel file is a single file contained on a single
reel of tape. The first block is the standard label;
this is followed by a tape mark. The data blocks come
next; the last data block is followed by a tape mark.
This tape mark is followed by an EOF trailer label
and then another tape mark.
On 7340 tapes, both header and trailer labels must
be written in the unpacked mode, regardless of the
mode in which the data records are written.
Multi - File Reel
NOTES ON STANDARD LABEL FORMAT
A multi-file reel is a single reel of tape containing
two or more files. Each of these files is identical
to a single-reel file.
Multi-Reel File
A multi-reel file is a single file contained on two or
more reels of tape. Each reel of a multi-reel file
is identical in format to a single-reel file except that
all reels but the last one have EOR trailer labels.
The last reel of the file has an EOF trailer label
instead of aILEOR trailer label.
Checkpoint Blocks on Data Tapes
The manner in which checkpoint blocks are recorded
on data tapes is specified in Field 19 of the standard
label.
HEADER LABE LS
When a tape is entered into a system of labeled tapes,
the new tape should have a header label followed by
a tape mark. The header label should contain
information in the Label Identifier and Reel Serial
Number fields only (see the format description
below).
TRAILER LABE LS
On 729 II, III, IV, V, and VI tapes and 7330 tapes,
only the Label Identifier and Block Count fields are
written in the trailer label. 7340 tapes contain the
above two fields in the trailer label and, in addition,
may contain any other trailer label fields because
of the ability of the 7340 to read backward.
No trailer label field on any tape, other than the
field entitled "For Optional Usage", is available to
the user for additonal label information; this is true
even if the fi~ld is not being used in the label.
1. Decimal notation is to be used in all label fields
containing numerical data.
2. Positions 6, 36, and 41 of the standard label are
not to be used. The user is not to assume that these
positions will remain blank at all times.
STANDARD LABEL FORMAT
Field 1: Label Identifier
Positions: 1-5
The contents of this field identify the type of label as
follows:
Code
Meaning
1HDRb
Header label
1EOFb
End-of-file trailer label
1EORb
End-of-reel trailer label
Additional codes will be assigned by IBM as required.
Field 2: Retention Period
Positions: 7-10
The contents of this field indicate the number of days
(0001-9998) the file is to be retained after the
creation date. The field should contain 9999 for files
to which an expiration date is not applicable.
Field 3: Creation Date
Positions: 11-15
The contents of this field indicate the year and day
of the year the file was created. The year (00-99)
occupies the first two positions of the field, and the
day of the year (001-366) occupies the last three
positions of the field (e. g. , January 31, 1962 would be
be entered as 62031).
3
Field 4: File Identification
Positions: 16-25
Field 10: Checksum Indicator
Position: 46
The contents of this field are assigned by the user
and are unique to the file; this field identifies the
entire file. Field 4 contains ten alphameric
characters, including blanks.
The contents of this field indicate the presence of
or absence of checksums.
Code
Meaning
-0-Not applicable or no checksum
present
1-9
Will be assigned by IBM for
various types of checksums
Field 5: File Serial Number
Positions: 26-30
The contents of this field are identical to the contents
of Field 6 of the first or only reel of the file. This
field contains five alphameric characters, including
blanks.
Field 6: Reel Serial Number
Positions: 31-35
The contents of this field are assigned to the reel
when it enters the system. The field contains five
alphameric characters, including blanks. The reel
serial number normally is also written on the
physical label of the reel for visual identification.
Field 7: Reel Sequence Number
Positions: 37-40
This is a four-digit field whose contents (0001-9999)
indicate the order of the reel within a given file.
Field 8: Reserve
Positions: 42-44
This field is reserved for future use to indicate the
file number in a multifile reel. This file number
will be 1 in the label(s) associated with the first file
on the reel, and will be increased by 1 for each
succeeding file on the reel.
Field 9: Density Indicator
Position: 45
The contents of this field give the density of the file as
indicated by the programmed set density instruction.
(Density does not refer to packed and unpacked data. )
Code
Meaning
-0-Not applicable
1
Low density
2
High density
4
Field 11: Block Sequence Indicator
Position: 47
The contents of this field indicate the presence or
absence of block sequencing.
Code
Meaning
-0Not applicable or no block sequence
field used
1-9
Will be assigned by IBM for various
types of block sequence fields
Field 12: Tape Checking/Interpreting Indicator
Position: 48
The contents of this field indicate how bits are written
on the tape to provide a means of verifying and/or
interpreting the data read from the tape.
Code
7030
Others
-1Single odd parity without Binary
Error Correction Code
2
Single even parity without BCD
Error Correction Code
3
Single odd parity with
Not applicable
Error Correction Code
Field 13: Tape Data Recording Technique Indicator
Position: 49
The contents of this field indicate the maximum number
of bits (not including check bits) that may be recorded
as a unit (byte) on the tape.
Code
Meaning
-6-729 or 7330
8
Hypertape
IBM will provide additional codes as they are required.
Field 14: Tape Data Processing Technique Indicator
Position: 50
Code
2
The contents of this field indicate the number of bits
(not including check bits) out of a byte that are to be
treated as a unit in processing. The Hypertape codes
are:
Code
Meaning
Each unit of data consists of four
4
bits (packed data).
Each unit of data consists of six
6
bits (unpacked data).
3
Field 15: Creating System
Positions: 51-54
The contents of this field denote the system that
created the file, e. g., 7074.
Field 16: Record Format
Position: 55
The contents of this field indicate the record format
of the file.
Codes will be provided by IBM as they are required.
Field 17: Record Length
Positions: 56-60
4-9
Meaning
Checkpoint blocks are interspersed
with data blocks.
Checkpoint blocks are written as
consecutive blocks. No data blocks
are written.
Will be assigned by IBM if required
to indicate additional ways of
recording checkpoint blocks.
Field 20: Block Count
Positions: 67-72
This field is used in trailer labels only. Its contents
indicate the number of physical tape records (blocks)
in the file that are used to record data. The block
count does not include header and trailer labels, tape
marks, segment marks, checkpoint records, or
other records not containing file data.
Field 21: Reserve
Positions: 73-74
This field is reserved for future use by IBM.
Field 22: For Disk Usage
Positions: 75-79
This field is not to be used in tape labels.
For fixed-length records, the contents of this field
give the number of characters per logical data
record; for variable-length records, the contents of
this field give the number of characters in the largest
possible logical data record of the file.
This field is reserved for future use by IBM.
Field 18: Blocking Factor/Size
Positions: 61-65
Field 24: For Disk Usage
Positions: 81-85
For fixed-length records, the contents of this field
indicate the number of logical data records within
each tape block; for variable-length records, the
contents of this field indicate the number of
characters in the largest possible tape block record
of the file.
This field is not to be used in tape labels.
Field 19: Checkpoint Indicator
Position: 66
The contents of this field indicate (1) the presence
and type or (2) the absence of checkpoint blocks.
Code
Meaning
-0-Not applicable or no checkpoint
block
1
Checkpoint blocks immediately
follow the tape mark that comes
after the header label. The checkpoint blocks are followed by a tape
mark and then the next data block.
Field 23: Reserve
Position: 80
Field 25: Reserve
Positions: 86-91
This field is reserved for future use as a field
containing cycle information.
Field 26: Reserve
Positions: 92-100
This field is reserved for future use by IBM.
Field 27: For Optional Usage
Positions: 101-120
This field may, at the user's option, contain additional
label data.
5
C28-8142
ALPHABETIC LISTING OF LABEL FIELDS
The label positions occupied by each field are given
in parentheses following the field number.
Field Name
Field Number &
Label Positions
Block Count
Block Sequence Indicator
Blocking Factor/Size
Checkpoint Indicator
Checksum Indicator
Creating System
Creation Date
Density Indicator
File Identification
File Serial Number
For Disk Usage
For Disk Usage
For Optional Usage
Label Identifier
Record Format
Record Length
Reel Sequence Number
20 (67-72)
11 (47)
18 (61-65)
19 (66)
10 (46)
15 (51-54)
3 (11-15)
9 (45)
4 (16-25)
5 (26-30)
22 (75-79)
24 (81-85)
27 (101-120)
1 (1-5)
16 (55)
17 (56-60)
7 (37-40)
Field Number &
Label PositionS';
Field Name
6 (31-35)
Reel Serial Number
8 (42-44)
Reserve
21 (73-74)
Reserve
23 (80)
Reserve
·25 (86-90)
Reserve
26 (91-100)
Reserve
2 (7-10)
Retention Period
Tape Checking/Interpreting
12 (48)
Technique Indicator
Tape Data Processing Technique
Indicator
14 (50)
Tape Data Recording Technique
13 (49)
Indicator
Note: Positions 6, 36, and 41 of the standard label
are blank.
1-SINGLE FILE REEL
DATA TAPE BLOCKS
2-MULTI-Fll.E REEL
FILE 2
FILE 1
3-MULTI-REEL FILE
Reel 1 of 2
FIRST PART OF FILE N
Reel 2 of 2
LAST PART OF FILE N
4-CHECK POINTS ON DATA TAPES*
T
M
H
D
R
CHECKPOINT
BLOCK
T
M
FILE N
T
M
EOF
OR
EOR
T
M
;n
?>
()
N
00
I
00
!i;:
N
*Must be used when files are to be interchanged between data processing systems.
Figure 1.
JJJ:ID~
(J)
International Business Machines Corporation
Data Processing Division, 112 East Post Road, White Plains, N. Y.
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