ORA-39346: data loss in character set conversion for object TABLE_STATISTICS

When doing export/import using data pump encountered below error. This happens when invalid or corrupt characters are stored in the database.

When using export/import instead of data pump, no errors reported.

Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS
Processing object type SCHEMA_EXPORT/TABLE/CONSTRAINT/REF_CONSTRAINT
Processing object type SCHEMA_EXPORT/TABLE/TRIGGER
Processing object type SCHEMA_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
ORA-39346: data loss in character set conversion for object TABLE_STATISTICS:"ORCL"."TABLE1"
ORA-39346: data loss in character set conversion for object TABLE_STATISTICS:"ORCL"."TABLEMAT"
Job "SYS"."SYS_IMPORT_SCHEMA_01" completed with 2 error(s) at Sun Apr 11 12:05:25 2021 elapsed 0 00:20:13

After research found that this is a known issue due to Bug 13696958 .

The fix for Bug 13696958 

added warning messages in 12.1 datapump import for characters that couldn't be converted. Previously, a fix for Bug 16173664 was made available to report the affected object in the import log.

Workaround/fix:-

Needs to apply interim patch 21342624 
and execute post-install step:

$ datapatch

If the patch 21342624 installed then impdp log will report the objects that are experiencing data loss during characterset conversion. If the fix then character data is checked even when the client and database character sets are the same, to prevent input of invalid character data.

That being said the fix for Bug 21342624 does not stop the error messages or repair any bad data on the source database

In case of any further issues , patch questions or concerns, please contact Oracle Support.

Refer Oracle support notes: -

Unpublished Bug 21342624 - DATA LOSS DUE TO CHARACTER SET NOT SHOWING CORRECT SET OF OBJECTS DURING IMPORT.

Note 1317012.1 - How To Use MOS Patch Planner To Check And Request The Conflict Patches?

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