VSAM provides you with several means of locating problems in your catalogs and data sets. You can also use the access method services REPRO command to copy a data set to an output device.
The access method services VERIFY command provides a means of checking and restoring end-of-data-set values after system failure.
That means if any of the files improperly closed, they will be corrected and closed by ‘verify’ command.
The access method services EXAMINE command lets the user analyze and report on the structural inconsistencies of key-sequenced data set clusters. The EXAMINE command is described in Checking VSAM Key-Sequenced Data Set Clusters for Structural Errors.
The syntax for Verify command:
Note: If a VSAM data set was allocated in a JCL job but not opened, and another job deleted and redefined the same VSAM data set, then the first job will not be able to open the data set. An IDCAMS DELETE NOSCRATCH command does not serialize on SYSDSN/dsname resource when deleting and redefining the data set. Because the allocation is pointing to a specific UCB, if the PATH is deleted and redefined on another UCB, the subsequent OPEN fails because the new UCB may not match the original UCB in the TIOT entry.
The DIAGNOSE command to indicate the presence of nonvalid data or relationships in the BCS and VVDS, see z/OS DFSMS Managing Catalogs. (ref IBM)