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ORA 01555 "snapshot too old: rollback segment number %s with name \"%s\" too small" (Doc ID 1555.1)

Last updated on FEBRUARY 05, 2024

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.1 to 11.2.0.1 [Release 9.2 to 11.2]
Oracle Database - Enterprise Edition - Version 11.2.0.3 to 11.2.0.3 [Release 11.2]
Oracle Database - Enterprise Edition - Version 11.2.0.4 to 11.2.0.4 [Release 11.2]
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
Information in this document applies to any platform.

Purpose

This article discusses the error "ORA-1555", what it means and possible actions. The information here is only applicable to the versions listed and is provided only for guidance.

Scope

This note is intended for general audience as initial starting point for beginning diagnosis of ORA-1555.

Error: ORA 01555
Text "snapshot too old: rollback segment number %s with name \"%s\" too small"
----------------------------------------------------------------------------------------------
Cause: rollback records needed by a reader for consistent read are overwritten by other writers
Action: If in Automatic Undo Management mode, increase undo_retention setting. Otherwise, use larger rollback segments

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