When data is written to a tape, the name of the tape file, together with other features, is stored in the MAREN catalog entries of the tapes used. (Exception: This does not apply in the case of an save run involving a directory.) This makes it possible to determine which tapes contain a tape file (statement SHOW-VOLUME-ATTRIBUTES FILE-NAME=...).
The MAREN catalog contains several versions of a tape file if the same tape file was created at different times and using different tapes and if the relevant tapes have not yet been released in the MAREN catalog. These individual versions of a file are not distinguished by their file name, as are, for example, file generations.
The tapes belonging to a file version form a tape set in the MAREN catalog. Used in this context, however, the term “tape set” is only loosely related to the term as used in a number of BS2000 commands (e.g. CREATE-TAPE-SET).
The common feature of a tape set and thus of a file version in the MAREN catalog is the fact that in all associated tapes the fields FILE-NAME and FIRST-VOLUME are identical in the MAREN catalog, FIRST-VOLUME containing the archive number of the first tape to which this file version has been written.
The order in which data was written to the tapes when creating the file can be determined with the aid of the VOLUME-SEQUENCE catalog entry field. This catalog entry field is given the value 1 for the first tape, the value 2 for the second tape, etc.
If only one tape was required for the creation of a tape file, the tape set then consists of a single tape and no additional tapes are required to access this file version.
In addition, there are other catalog entry fields for each file on the tape which MAREN evaluates when determining a file version. These include:
- CREATION-DATE: Date when a file was last written to the tape.
- CREATION-TIME: Time when a file was last written to the tape.
- CLOSE-INDICATOR: Indicator showing whether the tape was properly closed when the tape file was created.
- USER-IDENTIFICATION: User ID to which the tape is assigned in the MAREN catalog. However, this catalog entry field is relevant only if selection is to be based on user IDs.
- DEVICE-TYPE: If a device type was specified explicitly in the IMPORT-FILE (or FILE) command, only MAREN catalog entries with exactly this device type are used to determine the file version.
Tape-sets can be addressed explicitly with various statements. The MODIFY-TAPE-SET-ATTRIBUTES statement is available as a special statement for modifying MAREN catalog entries for a tape file.