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The CTTTPI utility can produce a detailed report about the logical and physical content of a volume including logical files, labels, tape marks and unreadable areas (I/O errors).
This function is especially useful when recovering files and/or data that have been partially overwritten on magnetic media (for example, a longer file partially overwritten by a shorter file or multifile volumes in which the first few files have been overwritten).
The tape mapping function is generally invoked as a started task using command
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This command invokes the CTTTPI utility with the single control statement
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The TAPEMAP function produces a report that contains a single line for each of the following elements:
Table 392 CTTTPI Elements
Element |
Description |
|---|---|
VOL1 |
Volume label |
HDR1 |
First part (and sometimes the only part) of a header label that describes a standard label data set |
HDR2 |
Second part of a data set label |
DATA BLOCKS |
Actual data portion of a file on the media |
EOF1 |
First part of a data set trailer label |
EOF2 |
Second part of a data set trailer label |
EOV1 |
First part of an End-Of-Volume tape label. This element appears when the preceding standard label data set continues on another volume. |
EOV2 |
Second part of an End-Of-Volume tape label |
Tape Mark |
Physical indication on the media that separates one physical file from another and separates standard labels from data. Two consecutive tape marks commonly determine the logical end of the recorded area on the media. |
I/O Error |
Area that could not be read by CTTTPI |
The TAPEMAP function reports information extracted from the above elements such as the data set name (meaning, the full data set name if it does not exceed 17 characters, or the last 17 characters of a longer data set name) creation date, creating job name, block size, physical and logical file sequence numbers.
Physical file sequence numbers are counted by tape marks. Each tape mark on the tape indicates an end-of-file. Logical file sequence numbers are extracted from HDR1. If there is no HDR1 on the tape (for example, an NL tape) the logical file sequence number is blank.
If a map of the complete media is requested (parameter STOP set to N, described later) data sets written beyond the present logical end of the recorded area can be examined.
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