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ORA-01555: Snapshot too old
What it means
A long-running query needed an old version of a block from undo to stay read-consistent, but that undo had already been overwritten. Frequent with fetch-across-commit (committing inside a cursor loop over the same table).
How to fix it
Do not commit inside cursor loops, make the query faster, and size undo/UNDO_RETENTION for the longest query. Process data in set-based statements instead of row by row.
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.