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ORA-1578 ORA-26040 in a LOB segment - Script to solve the errors (Doc ID 293515.1)

Last updated on OCTOBER 04, 2022

Applies to:

Oracle Database - Standard Edition - Version 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
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.
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***Checked for relevance on 29-Jul-2020***



The purpose of this article is to provide a script to update a lob column, that is referencing a lob block marked as corrupted due to NOLOGGING operations, with an empty lob.

It will avoid errors ORA-1578 / ORA-26040 when the lob column is accessed by a sql statement like a SELECT and a table export can be produced if needed.


ORA-1578 and ORA-26040 are produced when reading a lob column in a table:


When ORA-26040 is not produced along with ORA-1578 the block is then corrupt by a different reason and Block Media recovery can be used to repair the corruption like RMAN BLOCKRECOVER (BMR).


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In this Document
 1. Query dba_extents to find out the lob segment name.
 2. Query dba_lobs to identify the table_name and lob column name:
 3. Identify the table rowid's referencing the corrupted lob segment blocks by running the following plsql script:
 4. Update the lob column with empty lob to avoid ORA-1578 and ORA-26040:
 5. Observations

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