This chapter describes how you can analyze your catalogs of DASD data sets. Proper catalog functioning requires that the structure of the BCS remain sound. It also requires that data set information contained in the BCS, VVDS, and VTOC be synchronized. That is, the characteristics of a data set (extent information, SMS class names, etc.) must be the same in the data set's entries in the BCS, VVDS, and VTOC.

Structurally damaged or unsynchronized catalogs can cause jobs that use the catalog to fail or produce incorrect results if the wrong data set is processed. If the number of corrupt entries becomes large, you might have to recover the catalog.

It is strongly recommended that you perform the DIAGNOSE and EXAMINE functions regularly for all catalogs in your installation. They can be combined with regular backup functions, for example. Performing these functions regularly ensures that backups taken of catalogs are structurally valid and also helps identify, as early as possible, when a catalog has possibly been damaged.