I have two databases. They both have the same schemas. One is approx. 1GB and the other is approx. 10GB. On both databases, there is a parent and child table with similar number of records (~300k records each). From legacy code, the previous DBA disabled a foreign key constraint, did some INSERTs into the parent and child tables and then re-enabled the foreign key. On the smaller database, this operation takes < 1 second. On the larger database, this operation takes 1.5 minutes. After timing each instruction, I narrowed it down to the re-enable causing the bottleneck, but I don't know exactly why it's <1 second on one instance and 1.5 minutes on the other. I think it's due to the size. But I'm not sure how to substantiate this to my manager. I cannot use EXPLAIN PLAN. Is there a way to quantify or determine what's causing the discrepancy in timing?