I know that it may seem confusing on oracle-l, but 'select' doesn't ONLY refer to the SQL language - in that case, it has to do with I/O multiplexing - try 'man select'. Identifying what your file descriptors are pointing to might help. In any case, you are more likely to see things with sar or iostatthat the V$ views, as you pointed. Regards, Stephane Faroult RoughSea Ltd http://www.roughsea.com On Tue, 23 Nov 2004 05:25 , New DBA <new_dba_on_the_block@xxxxxxxxx> sent: Tony, Yes if Oracle is not waiting but working no wait will be registered. But it should atleast be reflected in "CPU used by this session" stat. It doesn't. I traced a few processes, but the trace files show no SQL which takes lots of CPU. Moreover, the CPU utlization in the trace file, or in v$sesstat don't match with the actual CPU taken by the process as seen from the OS commands like "top" Thats why I believe its some kind of O/S issue. So I did a truss on the process. And I saw the following line repeating infinitely. select(2048, 0x800003fffdffb3d0, 0x800003fffdffb4d0, 0x800003fffdffb5d0, 0x800003fffdffb6d0) = 0 I'm not sure how to interpret the output of truss, so I posted it in this forum since there are many experts out here, who might be able to interpret it! Is there any further information I can gather at the O/S level which throws some light on the problem? As far as statspack is concerned, we haven't implemented statspack, but I did run utlbstat/utlestat and uploaded the output to oraperf.com. It didn't suggested or detect excess CPU/LIOs, since those stats are pretty acceptable in the trace files. Regards New DBA --- Tony.Adolph@xxxxxx[1] wrote: >I'm no expert here, but here *may be* a few things >to think about: > >When Oracle is actually doing something it isn't >recorded as a wait event, >e.g. getting a datablock that is in cache doesn't >generate a wait event. >If your query is "horrible" you could be using loads >of CPU without >generating many waitevents. > >A little more dodgy info: "db file sequential >read" is normally >accociated with datafile access by rowid, ie. after >an index lookup. > >I think I'd try to find out which queries are >running during the >performance problem times and explaining the >queries. > >Also, have you run spreport for this time period? > >Told you I wasn't an expert, but I hope that prompts >other readers to fill >in the gaps and give you better hints, > >Good luck >Tony __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com[2] -- //www.freelists.org/webpage/oracle-l[3] --- Links --- 1 javascript:parent.opencompose('Tony.Adolph@xxxxxx','','','') 2 modules/refer.pl?redirect=http%3A%2F%2Fmail.yahoo.com 3 modules/refer.pl?redirect=http%3A%2F%2Fwww.freelists.org%2Fwebpage%2Foracle-l -- //www.freelists.org/webpage/oracle-l