ORA-01555 "Snapshot too old" - Detailed Explanation
(Doc ID 40689.1)
Last updated on JULY 05, 2023
Applies to:
Oracle Database - Enterprise Edition - Version 9.2.0.8 and later Oracle Database Cloud Schema Service - Version N/A and later Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later Oracle Cloud Infrastructure - Database Service - Version N/A and later Oracle Database Cloud Exadata Service - Version N/A and later Information in this document applies to any platform.
Purpose
This article will discuss the circumstances under which a query can return the Oracle error ORA-01555: snapshot too old: rollback segment number string with name "string" too small. The article will then discuss actions that can be taken to avoid the error and finally will provide some simple PL/SQL scripts that illustrate the issues discussed.
Scope
It is assumed that the reader is familiar with standard Oracle terminology such as 'rollback segment' and 'SCN'. If not, the reader should first read the Oracle Database Concepts manual and related Oracle Database documentation.
Details
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