VSAM OPEN calls VERIFY when it opens a catalog.

You cannot use VERIFY to correct catalog records for a key-sequenced data set, or a fixed-length or variable-length RRDS after load-mode failure. An entry-sequenced data set defined with the RECOVERY attribute can be verified after a create (load) mode failure; however, you cannot run VERIFY against an empty data set or a linear data set. Any attempt to do either will result in a VSAM logical error. For information about VSAM issuing the implicit VERIFY command, see Opening a Data Set.