Re: V$SYSTEM_WAIT_CLASS

On Aug 13, 12:10 am, dean <deanbrow..._at_yahoo.com> wrote:
> 10g
>
> select * from V$SYSTEM_WAIT_CLASS order by TIME_WAITED desc;
>
> WAIT_CLASS_ID WAIT_CLASS# WAIT_CLASS TOTAL_WAITS TIME_WAITED
> ------------- ----------- -------------- ----------- -----------
> 2723168908 6 Idle 15742538 990583927
> 1740759767 8 User I/O 1501104 541245
> 2000153315 7 Network 35587647 227757
> 4108307767 9 System I/O 690084 194154
> 3386400367 5 Commit 70951 23803
> 3875070507 4 Concurrency 11212 13790
> 4217450380 1 Application 12112 5730
> 1893977003 0 Other 7106 5411
> 3290255840 2 Configuration 171 1979
>
> This is the first time I have looked at this view, and I'm trying to
> understand it - does this indicate performance issues with the disk i/
> o?
>
> Thanks!
>
> Dean

Not necessarily; the TIME_WAITED values are in centiseconds (1/100 of a second) and are cumulative for all sessions for as long as the database is running uninterrupted. The User I/O number you posted represents roughly 90 minutes of wait time for ALL sessions since the database started. Presuming you have more than one connected session and that the database has been up and running for more than two hours I'd say no; follow Daniel's advice and file this away for future reference. When and if a user (or group of users) decides to complain about performance you can resurrect these values and compare them to the current numbers (again, presuming you haven't shut down the database between now and then) and possibly find the area or areas which have changed.

There is no need to create problems where none currently exist.

David Fitzjarrell Received on Mon Aug 13 2007 - 10:54:19 CDT