Catalog entries might become unsynchronized, so that information about the attributes and characteristics of a data set are different in the BCS, VVDS, and VTOC. These differences may make a data set inaccessible or otherwise unusable.

To analyze a catalog for synchronization errors, you can use the access method services DIAGNOSE command. With this command, you can analyze the content of catalog records in the BCS and VVDS, and compare VVDS information with DSCB information in the VTOC.

Besides checking for synchronization errors, DIAGNOSE also checks for invalid data, or invalid relationships between entries.

To use DIAGNOSE ICFCATALOG, you must have READ authority to the RACF® STGADMIN.IDC.DIAGNOSE.CATALOG profile if it is defined. DIAGNOSE VVDS requires READ authority to STGADMIN.IDC.DIAGNOSE.VVDS. See Storage Administration (STGADMIN) Profiles in the FACILITY Class for more information on STGADMIN profiles.

If you are using DFSMShsm, catalog synchronization is checked during the daily data management cycle, and synchronization errors are reported. This eliminates the need to use DIAGNOSE separately, unless you are recovering a catalog. Whenever you recover a catalog, use DIAGNOSE to help identify catalog records that must be updated or that are otherwise in need of individual recovery. Updating catalog records after recovery is discussed in Updating the Catalog After Recovery.