Toad World® Forums

Average Wait and Time Waited in Sessions view

I’ve been looking at the disk latency in our system and have looked at the time vs disk read values shown in SGA trace and in the Sessions view.
The Time waited and Average wait columns in the Total Waits breakdown of the Waits tab of the sessions view is a factor 10 lower than reality. The result is that my disks show an impressive 0.89 ms latency when, in reality, the value is 8.9 ms. The time waited micro is correct but the Time Waited column (presumably milliseconds?) and the Average Wait are 10X too small.
(Toad for Oracle Base 11.0.0.116)

Hi Matt,

Are you looking at Session Browser -> RHS -> Waits?

If so, we are just showing the data from Oracle. We aren’t doing anything
to change the units (or even display them). That data comes from the
v$session_event view, and according to 11g Oracle docs, the time_waited column
is microseconds.

http://docs.oracle.com/cd/E11882_01/server.112/e25513/dynviews_3020.htm

-John

looking at session browser -> Sessions -> Waits -> Total Waits (rather than current waits)
The Time Waited, Average Wait and Max Wait columns are the items that look wrong to me. Time Waited Micro has been divided by 10,000 rather than 1,000 ?

Well, according to that link I gave you below…Time_waited, max_wait,
average_wait are all in hundredths of a second. Time_waited_micro is
microseconds which is millionths of a second.

1/100 * 1/10000 = 1/1000000 = 1 millionth, so it seems right to me.

It would be nice to know what we are looking at here without having to go to
Oracle docs. And I’ve heard others complain about what an unusual unit
hundredths of seconds are.

Just to give Oracle’s seemingly odd choice an explanation. Remember that
Oracle has been around a long time and on many hardware/software platforms. A
long time ago hundredths of a second was as far as they could go portably
– so it became somewhat of a standard. No one likes it much –
including Oracle – but there is a reason for what seems like an odd choice
J

Ok, I added a “Time Units” to the toolbar there. It defaults to
Hundredths, as Oracle does, but you can change it to seconds or milliseconds if
you like. I think this will make it much more clear.

Thanks for that. I didn’t follow your link initially but it does make clear what the units are. RTFM applies I suppose but the point of a GUI is that it’s supposed to make things more intuitive.
Thanks for you time in dealing with this.