Advanced Authentication documentation link below calls for dropping of indexes for performance improvement.
On attempting to drop the index
SQL Error: ORA-02429: cannot drop index used for enforcement of unique/primary key
02429. 00000 - "cannot drop index used for enforcement of unique/primary key"
*Cause: user attempted to drop an index that is being used as the
enforcement mechanism for unique or primary key.
*Action: drop the constraint instead of the index.
How to resolve Dropping of an index on AA table - SQL Error: ORA-02429 ?
Database : Oracle
*** Note any constraint that is defined needs to be dropped as in the example below the Constraint/Primary Key (PK_ARUDS_USERAUDITLOG) is defined on the table ARUDSUSERAUDITLOG. This constraint has to be dropped before dropping the index. The example below uses syntax on a Oracle Database.
ALTER TABLE ARUDSUSERAUDITLOG DROP CONSTRAINT PK_ARUDS_USERAUDITLOG;
Once the Constraint is dropped the index can be dropped after that.
DROP INDEX PK_ARUDS_USERAUDITLOG;