The Audit data set is vital to the restore process. CA 1 provides absolute protection to ensure that available Audit data can always restore a damaged TMC to the point of failure. The Audit is formatted, or mapped, with a given number of Audit records (usually enough for two days worth of activity). CA 1 system option THAUDT defines a threshold level of Audit records. When this level has been reached, warning messages are issued to the console indicating a TMC backup is needed.
If the Audit records written since the previous backup actually reach the total allocation, CA 1 abends all tape requests until such time as a TMSCOPY backup can be executed. In this manner, CA 1 can consistently restore a TMC to a point of failure without loss of database integrity, because there is no chance that the Audit data set does not contain all transactions since the previous backup.
If TMC backup processing is carefully planned, the Audit threshold should never be reached. The Audit data set is designed to continue recording transactions even when the TMC backup is running. There is no operating system interference and no need to interrupt tape processing during the TMSCOPY backup execution.
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