ORA-01502: index 'Schemaname.indexname' or partition of such index is in unusable state

Hi All,

We are getting following error when we try to exceute DELETE statementto to remove millions of rows in a table  after making index to unusable state.

ORA-01502: index 'Schemaname.indexname" or partition of such index is in unusable state

We followed foolowing approach to delete millions of rows in a single table as per retention policy.

First we made index which is pointing to that table as unusable state.

Second we executed delete statement in PL/SQL bock.

I have seen that INDEX is unique index, because of that we are getting this issue.

Could anyone guide me how to resolve this issue.