ERROR: ORA-01408 such column list already indexed

ERROR

ERROR: ORA-01408 such column list already indexed while upgrading database to 11.2.0.4 using DBUA

SOLUTION

Prior starting the upgrade drop the index in the SYSTEM Schema

drop index system.REPCAT$_AUDIT_COLUMN_IDX1;

Start the upgrade
./dbua

If the index is not dropped prior starting the upgrade, when the issue is faced drop the index and ignore the error so the DBUA may continue if no other errors are faced in the DBUA completion, recreate the index using below command

create index system.repcat$_audit_column_f2_idx on system.repcat$_audit_column (base_sname,base_oname,base_conflict_type_id, base_reference_name);