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 >