You can't base it solely on size; it also depends upon how many columns are indexed as each requires a full table scan to gather data. David Fitzjarrell ________________________________ From: Ingrid Voigt <giantpanda@xxxxxxx> To: oracle-l@xxxxxxxxxxxxx Sent: Wednesday, June 5, 2013 8:56 AM Subject: Running time of index rebuild Hi, does anybody know how the running time for index create or rebuilds inOracle changes withnumber of lines / table size? I would expect O(n log n)? We need a guesstimate for the time for a complete rebuild where the test environment is considerably smaller: TEST: 19 mio rows / 16 GB / 15 minutes PROD: 894 mio rows / 725 GB / ??? Refilling test with complete production data is not an option. I know that index rebuilds are not usually necessary. In this case we need to gain enough space in the database to last until the new SAN is usable, and 50 GB (as predicted by the segment advisor) would be very helpful. My suggestion for the maintenance window an prod would be 16 hours, do you have a better idea? Best regards IngridVoigt -- //www.freelists.org/webpage/oracle-l -- //www.freelists.org/webpage/oracle-l