Sometimes a data set is closed properly, but an error occurred. The most likely error is an incorrect high RBA in the catalog. Other possible errors are an incomplete write to a DASD or duplicate data exists. One way to avoid these errors is by doing synchronous direct inserts. Another way is by using abnormal termination user exits in which you issue a CLOSE (perhaps with the TYPE=T parameter) to close the data set properly.

If you suspect that a write operation is incomplete, issue either an IMPORT or REPRO command to get an old copy of the data. Intermediate updates or inserts are lost. You must have an exported version of the data set available to use IMPORT. Use a backup copy for REPRO.

Duplicate data in a key-sequenced data set, the least likely error to occur, can result from a failure during a control interval or control area split. To reduce the number of splits, specify free space for both control intervals and control areas. If the failure occurred before the index was updated, the insert is lost, no duplicate exits, and the data set is usable.

If the failure occurred between updating the index and writing the updated control interval into secondary storage, some data is duplicated. However, you can access both versions of the data by using addressed processing. If you want the current version, use REPRO to copy it to a temporary data set and again to copy it back to a new key-sequenced data set. If you have an exported copy of the data, use the IMPORT command to obtain a reorganized data set without duplicate data.

If the index is replicated and the error occurred between the write operations for the index control intervals, but the output was not affected, both versions of the data can be retrieved. The sequence of operations for a control area split is similar to that for a control interval split. To recover the data, use the REPRO or IMPORT command in the same way as for the failure described in the previous paragraph.

Use the journal exit (JRNAD) to determine control interval and control area splits and the RBA range affected.