If errors are NOT reported, the data set is not corrupted. A read and update process overlapped and the read process got bad data as the update was changing data at the same time. If errors ARE reported, the data set is corrupted.
Recover the corrupted data set
Restore the data set
Refresh LLA, if data set was LLA-managed
Identify what corrupted the data set
Most of the time a corrupted data set will be due to an update process not serializing the data set. After you have recovered the data set, you should get an $UPDATE rule with ENQCHECK=W created (or just add ENQCHECK=W if $UPDATE rule already exists). ENQCHECK=W will cause PDSMAN to check every STOW for a proper enqueue. If the enqueue is not present, PDSMAN will issue a PDSM021-10 message and let the job continue.