Data not Migrated Properly While Using DBMS_REDEFINITION
(Doc ID 1620561.1)
Last updated on FEBRUARY 03, 2020
Applies to:Oracle Database - Enterprise Edition - Version 220.127.116.11 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.
***Checked for relevance on 01-Mar-2017***
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
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