The Automatic Pointers Error Correction (APEC) subtask of the Common Tape System (CTS) is provided to inspect and repair volume and data set chaining errors found in the CA 1 TMC in real-time. The APEC subtask (program TMSAPEC) and TMSPTRS batch utility may both be used to identify invalid internal CA 1 multivolume and multi-data set chains and errors that exist in the free chain of unused DSNBs. In most cases invalid or broken chains may occur as a result of invalid manual updates, however a system failure during CA 1 processing may also cause invalid chains, or if the TMC could not be restored with all available Audit data (as in a disaster recovery). Volumes in delete or scratch status are not processed for pointer errors.
Note: For a description of volume and data set chaining structures and possible errors, see TMSPTRS in the Utilities and Reports Reference Guide.
Unlike TMSPTRS, which scans for pointer errors, generates reports, and control statements, the TMSAPEC program can identify additional problems and is able to correct pointer errors directly in the TMC. APEC can also be run in a "NOUPDATE" mode, causing it to only report on errors found and to generate control statements for the TMSUPDTE, TMSUDSNB, and TMSAGGR utilities. In addition to the errors identified by TMSPTRS, APEC will also verify that all of the DSNBs on the free chain are truly free.
All messages created by TMSAPEC are in the same format as those created by TMSPTRS. Please note some messages may indicate a range of volumes or DSNBs, while messages from TMSAPEC are for a single volume or DSNB. Also note that because APEC is updating the TMC in real-time, the errors identified by APEC may differ from TMSPTRS. The following is a list of errors fixed by APEC: ERR24, ERR37, ERR41, ERR42, ERR43, ERR44, ERR45, ERR51, ERR55, ERR56, ERR78, ERR79, and ERR67. When APEC is run with the NOUPDATE option, one pointer error can cause the generation several messages. When run with the UPDATE option ON, the same pointer error may only generate a single error message.
APEC is designed to be run as a background task that allows users to control how frequently and how long the task is to be run. Control statements are also provided to allow you to prevent the task from running during specified periods of high activity and pacing logic is provided to prevent over-utilization of CPU resources.
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