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ORA-00031: Session marked for kill
What it means
ALTER SYSTEM KILL SESSION could not end the session immediately (it is rolling back or waiting on an external call), so it was only marked.
How to fix it
Wait for the rollback to finish (v$transaction used_ublk decreases) or use KILL SESSION ... IMMEDIATE / DISCONNECT SESSION ... IMMEDIATE.
Catch it before it runs
ORA Error Helper
Explains ORA-/PLS- codes inside JetBrains IDEs and DataGrip. PL/SQL Lint
Flags risky PL/SQL patterns while you type. Oracle Plan Reader
Reads execution plans and points at the slow step. PL/SQL in Practice
Kindle book with practical PL/SQL for working developers.
Explains ORA-/PLS- codes inside JetBrains IDEs and DataGrip. PL/SQL Lint
Flags risky PL/SQL patterns while you type. Oracle Plan Reader
Reads execution plans and points at the slow step. PL/SQL in Practice
Kindle book with practical PL/SQL for working developers.
Nearby errors
Updated 2026-11-12.