ORA-01502: index or partition of such index is in usable state problem

I have a table in my Oracle database, where select pkcol, count(*) from myTable group by pkcol having count(*) > 1; yields PKCOL COUNT(*) ------- ---------- 1 2 2 2 Trying to remove the duplicate rows delete myTable where pkcol = 1; Yields: > ORA-01502: index 'MYTABLE.PK_MT' or partition of such index is in > usable state. I'm using Oracle.DataAccess.Client.OracleBulkCopy to fill the table. As far as I understand documentation from Oracle PRIMARY KEY constraints had to be checked. Obviously they are not checked, as I found by doing the same bulkcopy two times in succession which ended in duplicates in all row. Now I'm only using it after deleting all rows and I'm using a table with a similar primary key as source. As result I expect no problems. But embedded deep inside my MS Build scripts, I end up with just 2 duplicates out of 2210 rows. I guess that ignoring the primary key in the first place is a clear bug. No Bulkcopy should be allowed to ignore primary key constraints. **Edit:** Meanwhile I found, that the 2 conflicting rows where normally inserted by some script before bulkcopy was called. The problem reduces to my known problem, that bulkcopy doesn't check primary keys here.