Session are blocked by a session with Session ID=0 and State=“?” in Teradata
SessionID 0 is blocking other session and State Shows “?”.
Session 0 is an internal session which is a part of database software. It cannot be started from client. It should never be aborted because Aborting session 0 could result in a "zombi-lock" that cannot be cleared by a database reset.
When a backup/restore job going on then you can see SessionID 0 and State “?”. Also if a backup/restore job fails, HUT locks may be remained then you can see the reamined HUT logcs as session ID=9 and State “?”. You can release the HUT lock by “RELEASE LOCK” Command. For more information how to release HUT lock please visit