v$system_event

[fraze]

Can anyone tell me what period of time is recorded in the wait columns. I was under the impression it was 100ths of sec but I'm getting some seriuosly large average wait times if thats the case (e.g. 4003 for buffer busy waits, 7497 for direct path reads etc)

Cheers,

Fraze

[marist89]

Yes, definitely 1/100 of a second. See http://otn.oracle.com/docs/products/...3163.htm#11062 for details.

[sambavan]

Yes it is,

http://technet.oracle.com/docs/produ...3163.htm#11062

Sam

[fraze]

I know its very system dependant but if its hundreths doesnt 40 secs for a buffer busy wait seem excessively high? The majority of my average wait times for reads/write events range from 2000 - 7000 (20secs to 70 secs!!).

The only reason I'm querying it is I've just found this
in the Oracle documentation for buffer busy waits:

"Wait time: Normal wait time is 1 sec. If the session was waiting for a buffer during the last wait, then the next wait will be 3 seconds."

This ties in with a figure of 4000 for buffer busy waits if its in 1000ths of a sec but shows I've got serious problems if its in 100ths!!!

[marist89]

Depends, what's your average wait time? 4 seconds waited if your instance has been up 40 days is nothing to worry about.

[fraze]

The figures posted are the average wait times, not the total.

[marist89]

Ah, got ya.

Yes, those do seem like high wait times. You may want to investigate I/O contention issues as well as tuning the DBWR processes.