My Oracle Support Banner

Data not Migrated Properly While Using DBMS_REDEFINITION (Doc ID 1620561.1)

Last updated on JANUARY 30, 2022

Applies to:

Oracle Database - Enterprise Edition - Version and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Information in this document applies to any platform. This Article is created to clarify the syntax of col_mapping parameter values in the START_REDEF_TABLE procedure of DBMS_REDIFINATION. DBMS_REDEFINITION misses data for nullable Column or those fields gets updated with NULL value and column with DEFAULT losses its original data


After running the DBMS_REDEFINITION few of the columns got updated with NULL or the column data is getting deleted and the column with DEFAULT will lose its original data and get the default value. This will cause the logical corruption in the existing data, as this is deleting data or changing the data.

The behaviour is demonstrated in the below testcase (Which is causing the Issue/Problem, which seems like delete the column data)

Part 1: Preparation



To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.