Cold, hard experience. Bug 2530125 Hang possible with "enqueue hash chains" latch held during deadlock detection Or, as described to me by Oracle Support about 3 years ago, "Deadlock detection dumps the processstate while holding the 'parent+children enqueue hash chains' latch which can cause the blocking symptoms you describe while the processtate is dumped. " Supposedly fixed in 9.2.0.7 and 10.1.0.2. I don't believe Sachin mentioned what version he was on. > holding a latch and doing file I/O ? Where did you get that idea? -- //www.freelists.org/webpage/oracle-l