DIAGNOSE checks the content of BCS and VVDS records in the following order:

1. entry or record format
2. any associations (in the BCS only)
3. miscellaneous length and context
4. BCS and VVDS dependencies (if the COMPARE DD option is specified)

DIAGNOSE issues message IDC21364I if errors are discovered in any of these steps. However, once an error is discovered, DIAGNOSE stops processing that entry, and proceeds to the next entry. Thus, additional errors might be hidden.

Because the DIAGNOSE command checks the content of catalog records, if the records contain corrupted information, there is the possibility that the DIAGNOSE job will abend. For example, corrupted length field values could lead DIAGNOSE to attempt to access invalid storage. If DIAGNOSE abends because of corrupted data in the catalog, try to determine the incorrect record, delete it, and recover the data set from a backup copy.

Another point to keep in mind is that DIAGNOSE can indicate that an entry is in error if another job is processing the entry at the same time as DIAGNOSE. For example, if DFSMShsm is migrating a data set while DIAGNOSE is checking the entry for the data set, you might receive an error for the entry. If you suspect that a DIAGNOSE indicated error is erroneous, use DIAGNOSE again and specify the entry in the INCLUDE parameter.