CA TLMS uses a highly sophisticated chaining technique to link volume base records that are created when multivolume data sets are created. Chains are broken and returned under normal operating conditions according to the value specified for the BRKCHN system option (see BRKCHN= Break Volume/Data Set Chains). The option can be specified as one of the following:
The chain is broken when a CLOSE is performed on one of the tapes. Specifying CLOSE should only be considered for special processing.
Note: This option is supplied for compatibility with earlier versions and must only be used in special circumstances. Note that chains will still be broken at OPEN, regardless of this option being specified.
A chain is broken when one of the volumes in the original chain is opened for output. Each volume within the chain becomes a single volume and all chaining fields (with the exception of tape history) in the associated VMF records are reset. This is the default.
All chains are broken when the tape is scratched, and previous information (with the exception of tape history) is reset. If a tape is scratched in error, the chain cannot be recreated by unscratching.
The volume chaining verification procedure (CATVCVS) checks the validity of the links between volume base records. This procedure should be executed on a daily basis. (The CATVCVS procedure is detailed in this chapter under "Verifying Volume Master File Chains" on Verifying Volume Master File Chains.)
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