Oracle Solution for Error ora-08111

Solution for Oracle Error ORA-08111

ORA-08111: a partitioned index may not be coalesced as a whole

What triggered the Error:

User attempted to coalesce a partitioned index using ALTER INDEX COALESCE statement, which is illegal

What should we do to fix it:

Coalesce the index a (sub)partition at a time (using ALTER INDEX MODIFY (sub)PARTITION COALESCE)