What is optimizer_mode set to? Have you tried the query with a /*+ RULE */ hint? Have you considered gathering statistics on the data dictionary? -Mark -- Mark J. Bobak Senior Oracle Architect ProQuest Information & Learning For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. --Richard P. Feynman, 1918-1988 -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Ebadi, Abdul Sent: Thursday, March 23, 2006 12:20 PM To: oracle-l@xxxxxxxxxxxxx Subject: Performance Problems We have a large datawarehouse database on Oracle and are encountering strange performance problems. A query such as "select count(*) from dba_data_files;" will run in a few seconds or as long as 15 minutes depending on when this is run. We've narrowed it down to where it is not even directly related to load on the DB. A few days ago, I ran this query right after we started the DB (no activity in the DB at all) and it took 6 minutes! The waits we were seeing were "db file sequential read" and "buffer busy wait" for this query. Keep in mind our DB is ~27TB with ~30,000 datafiles! Oracle 9.2.0.4 on Solaris 10. Any help will be appreciated. Thanks! -- //www.freelists.org/webpage/oracle-l -- //www.freelists.org/webpage/oracle-l