Common Tape System › CA 1 Automatic Pointers Error Correction (APEC)

CA 1 Automatic Pointers Error Correction (APEC)

Use the Automatic Pointers Error Correction (APEC) subtask of the Common Tape System (CTS) to inspect and repair volume and data set chaining errors found in the CA 1 TMC in real time. Use the APEC subtask (program TMSAPEC) and TMSPTRS batch utility 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 more information about volume and data set chaining structures and possible errors, see 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 also verifies 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. Some messages may indicate a range of volumes or DSNBs, while messages from TMSAPEC are for a single volume or DSNB. Because APEC is updating the TMC in real time, the errors identified by APEC may differ from TMSPTRS. The following errors are 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 run as a background task that allows users to control how frequently and how long the task is to be run. Use control statements to prevent the task from running during specified periods of high activity and pacing logic is provided to prevent over-utilization of CPU resources.