There is a startup parameter called timed_os_statistics, carrying a warning in the manuals that said:
Note: Gathering OS statistics is very expensive. Oracle Corporation recommends that you set this parameter in an ALTER SYSTEM statement rather than in the initialization parameter file, and that you reset the value to zero as soon as the needed statistics have been gathered.
My memory is that when you set this parameter, a session could call the operating system for O/S statistics relating to the work done and populate some extra statistics in the v$sesstat and v$sysstat view.
The statistics were class 16, and all had names starting with “OS”, and the advisory was that you set the parameter to a value in seconds which would dictate the length of time between calls for OS stats (although Metalink note 47360.1 has an interesting historical comment about Oracle 7).
A couple of odd things though:
- I’ve noticed that there are NO such statistics available in my Windows databases (even hidden in the x$ under the v$), even back in 18.104.22.168
- I’ve seen a couple of cases (Solaris I think) where the OS stats are populated even when timed_os_statistics = 0.
So posisbly some platform specific changes have been made to the feature since it first came out, but no-one has been assigned to update any of the related documentation.
Does anyone have any better information ?