If you're going to post to the list, I'd personally rather address someone with a name. (From my own skeptical mind I want to question the motive behind not giving a real name, or semi-real name) You're questions show a pretty good understanding of some underlying principles - so I'm a little concerned what your angle is. Again, it may just be my skepticism, or you may in fact be angling for some information to use in a manner inconsistent with the principles of this list. Chris Taylor Sr. Oracle DBA Ingram Barge Company Nashville, TN 37205 Office: 615-517-3355 Cell: 615-663-1673 Email: chris.taylor@xxxxxxxxxxxxxxx<mailto:chris.taylor@xxxxxxxxxxxxxxx> CONFIDENTIALITY NOTICE: This e-mail and any attachments are confidential and may also be privileged. If you are not the named recipient, please notify the sender immediately and delete the contents of this message without disclosing the contents to anyone, using them for any purpose, or storing or copying the information on any medium. From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Oracle Dba Wannabe Sent: Tuesday, December 07, 2010 10:36 AM To: oracle-l@xxxxxxxxxxxxx Subject: Is my Oracle Server issuing more IO than it can handle Hi All, this is a 10.2.0.4 single instance database (non asm). I see the following events from awr (1 hour snapshot - however hourly snapshots after this show the same trend with respect to wait events): Event Waits Time(s) Avg Wait(ms) % Total Call Time Wait Class free buffer waits 17,926,869 193,146 11 67.7 Configuration log file switch (private strand flush incomplete) 41,550 30,538 735 10.7 Configuration log file sync 211,675 25,156 119 8.8 Commit buffer busy waits 42,093 23,218 552 8.1 Concurrency db file parallel write 376 14,274 37,963 5.0 System I/O I know that db file parallel write only contributes to 5% of the total call time - but its avg wait time looks extremely poor - that and the fact that free buffer waits appear at top indicate that there's a db writer issue (db_writer_processes=4) - which leads me to believe perhaps its the IO subsystem. Now the storage team report there is nothing up with the storage. I was hoping someone could help with the following questions: 1. Is there someway from awr that I can determine that the Oracle server is issuing more IO than the storage system can handle for example: Physical reads: 954.74 16.68 Physical writes: 418.89 7.32 Phy Reads + Phy Writes = 1372 IOPS Can I then say that if each disk can do 100 IOPS, that the storage system should at least have 13 Disks? (13x100 IOPS)? Or is that an over simplification? 2. Interestingly this DB server was moved onto a new box with a different storage and the issue is no longer observed there. Transactions Per Second on old box = 57.22 Transactions Per Second on new box = 225 Phy Reads + Phy Writes for New Box, are slightly under half compared to the old box: Physical reads: 243.02 1.08 Physical writes: 564.62 2.51 That said, the redo size per second on the new box is twice that of the old box (7mb/s : 3mb/s). The buffer cache and db writer processes are the same on both boxes. Other than the storage aspect of things, I'm thinking (and will check) whether theres an o.s/kernel misconfiguration w.r.t to async io, etc that might be causing this on the old box. Appreciate any thoughts on 1 or/and 2 Thanks