IBM standard data set label 2 (HDR2/EOV2/EOF2)
The IBM® standard data set label 2 (HDR2/EOV2/TRL2) is 80 characters in length and the program uses it to identify additional information about the data set.
Table 1. Format of the IBM Standard Data Set Label 2 (HDR2/EOV2/EOF2) Offset Data type Length Contents 0 Character 3 Label identifier 3 Character 1 Label number 4 Character 1 Record Format 5 Character 5 Block Length 10 Character 5 Record Length 15 Character 1 Tape Density/Format 16 Character 1 Data Set Position 17 Character 17 Job/Job Step Identification 34 Character 2 Tape Recording Technique 36 Character 1 Control Character 37 Character 1 Reserved 38 Character 1 Block Attribute 39 Character 3 Reserved 42 Character 5 Device Serial Number (not used) 47 Character 1 Checkpoint Data Set Identifier 48 Character 22 Reserved 70 Character 10 Large Block Length
The program records the data set label in EBCDIC.
The program describes the contents and function of each of the following fields.
- Label identifier The characters identify the type of data set label.
- HDR
- Header Label (the beginning of a data set)
- EOF
- Trailer Label (the end of a data set)
- EOV
- Trailer Label (the end of a data set that is continued on another volume)
- Label number
The relative positions of this label within the set of labels of the same type. The Label number is always 2 for the IBM data set label 2.
- Record Format An alphabetic character that indicates the format of the records in the data set. While the operating system reads from the tape, the Record format field tells the operating system how to interpret the blocks of data the program reads.
- F
- Fixed length records
- V
- Variable length records
- U
- Undefined length records
- Block Length
A number indicating the block length (in bytes) of the data blocks on the tape. The number in this field can range from 18 to 32 767 on i5/OS®. For numbers greater than 32 767, the Large Block Length field allows values up to 512 KB.
- Record Length A number that indicates the record length, in bytes, of the logical records on the tape volume. The interpretation of the number depends on the Record Format field.
- F
- Fixed length records.
- V
- Variable length records.
- U
- Undefined length records
- Tape Density/Format A code indicating the record density/format of the tape volume.
- 3
- 1600 bpi
- 4
- 6250 bpi
- 5
- 3200 bpi
- blank
- all other densities/formats
- Data Set Position A code indicating a volume switch is as follows:
- 0
- No volume switch has occurred
- 1
- A volume switch previously occurred
- Job/Job Step Identification
This field identifies the job and job step that created or extended the data set. i5/OS does not use this field.
- Tape Recording Technique This field indicates the tape recording technique used in creating the data set.
- blank
- No Improved Data Recording Capability (IDRC) used.
- 'P '
- Improved Data Recording Capability (IDRC) used.
- Control Character A printer control code indicating whether the program uses a control character set to create the data set and the type of control characters used:
- A
- Contains ANSI control characters
- M
- Contains machine control characters
- blank
- Contains no control characters
- Block Attribute A code indicating the block attribute used to create the data set:
- B
- Blocked records
- S
- Spanned records, if the record format byte is V
- S
- Standard records, if the record format byte is F
- R
- Blocked and spanned records, if the record format byte is V
- R
- Blocked and standard records, if the record format byte is F
- blank
- Records that are not blocked and not spanned, or records that are not blocked and not standard
- Device Serial Number (not used)
The serial number of the device that writes the volume. Header and trailer labels can have different serial numbers if the program extends the data set. i5/OS does not use this field.
- Checkpoint Data Set Identifier
This byte contains the character C if the data set is a secure checkpoint data set. The byte is blank if the data set is not a secure data set checkpoint.
- Large Block Length
A number indicating the block length (in bytes) of the data blocks on the tape. The number in this field can range from 18 to 524288 on i5/OS. For numbers up to 32767, the Block Length field also contains the block length in bytes.
Parent topic:
Volume label fields