ORA-00031: Session Marked for Kill — What It Means and How to Fix It
ORA-00031 occurs when a DBA issues ALTER SYSTEM KILL SESSION but Oracle cannot terminate the target session immediately. Instead, Oracle marks the session as "KILLED" and waits for it to reach a safe termination point — typically after completing a rollback or releasing OS-level resources. This is less of a hard error and more of a transitional state that every Oracle DBA will eventually encounter.
Top 3 Causes
1. Large Transaction Rollback in Progress
When you kill a session mid-transaction, Oracle must roll back all uncommitted changes to preserve data integrity. The larger the transaction, the longer the session stays in KILLED status.
