I don't recall the cpu being heavily utilized - although i'll ask the os team for those stats too and check. this is what i see from the awr report - which appears to show the cpu is more idle than not: AVG_BUSY_TIME 36,662 AVG_IDLE_TIME 326,101 AVG_IOWAIT_TIME 157,442 AVG_SYS_TIME 17,481 AVG_USER_TIME 19,087 (1 hour snap, 5 CPU) Do any of you have any thoughts w.r.t to question 1 - whether those calculations can be representative of the disks i may need. thanks ________________________________ From: Niall Litchfield <niall.litchfield@xxxxxxxxx> To: okh@xxxxxxxxxxxxx Cc: "oracledbawannabe@xxxxxxxxx" <oracledbawannabe@xxxxxxxxx>; "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx> Sent: Tue, December 7, 2010 10:55:48 PM Subject: Re: Is my Oracle Server issuing more IO than it can handle And finally the wait time for log file sync is way too high (like at least 1 if not 2 orders of magnitude) . This can be an indication of either poorly performing storage (I got to learn this when we had a client with a duff disk in a raid 5 array on which the redo logs had been located!) or due to CPU starvation. I don't believe it is ever a symptom of memory problems though.. Given your other stats, I'd *guess* at the disk subsystem, but want to take more observations. On Tue, Dec 7, 2010 at 5:05 PM, OKH <okh@xxxxxxxxxxxxx> wrote: There is also another thing. Your log files are too small and you have too few of them. I suppose your log files and data files share the same disk(s). > > > > > >Felix Castillo Sanchez > >Am 07.12.2010 um 17:35 schrieb Oracle Dba Wannabe <oracledbawannabe@xxxxxxxxx>: > > >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 >> >> -- Niall Litchfield Oracle DBA http://www.orawin.info