I believe Steve Adams once told me that the shareable latch feature is = not implemented on HP-UX. Cary Millsap Hotsos Enterprises, Ltd. http://www.hotsos.com * Nullius in verba * Upcoming events: - Performance Diagnosis 101: 10/26 Toronto, 1/4 Calgary - SQL Optimization 101: 10/18 New Orleans, 11/8 Dallas, 12/13 Atlanta - Hotsos Symposium 2005: March 6-10 Dallas - Visit www.hotsos.com for schedule details... -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx = [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Smiley John - IL Sent: Tuesday, October 19, 2004 3:31 PM To: 'Oracle-L (E-mail)' Subject: CBC Latch contention in 10g I'm seeing large numbers of CBC latch waits when many sessions (20-40) = run the same SELECT statement simultaneously (I can peek at v$session_wait = and catch this many sessions waiting on latch free: cache buffers chains for = the same sql_id). CBC latch children have been sharable in read mode since 9i. I didn't = see any DML taking place at the same time that would cause these latches to = be taken in exclusive mode, so I'm wondering why they're blocking on the = CBC latches. I've examined the CBC latch children with the most sleeps and examined the blocks on their hash chains and found exactly what I = expected to find: hot blocks on some of the tables referenced in the queries. = But if the latches are truly sharable for CR buffer gets, this shouldn't cause = them to pile up on the latch. Assuming delayed block cleanout isn't the = problem, what might explain this? I've searched MetaLink for latch related bugs = in 10.1.0.2. No dice.=20 John Smiley -- //www.freelists.org/webpage/oracle-l -- //www.freelists.org/webpage/oracle-l