Daniel,
The one tuning tip that will make the largest beneficial impact is to make sure you are running with ECPS enabled.? In your Hercules configuration file, ensure that you have a line that says ECPSVM YES
Also, ensure that your V=R area is large enough.? I use an 8M area.
After MVS is IPLed as a guest, there are two other things you can do that will help by a small amount. These collectively might boost performance by another 1-2%.? From the MVS userid's virtual machine console, type in:
#CP SET NOTRAN ON
and then:
#CP SET STB VR
Both of these commands are reset at IPL, so that is why you must reissue them after IPL.? The NOTRAN ON setting tells CP that your guest is running V=R and that it no longer needs to provide CCW translation for i/o's that MVS issues.? The STB VR setting tells CP that it no longer needs to provide shadow page table maintenance for MVS because it is running V=R.??? CP knows that MVS is running V=R but nevertheless you must manually turn these options on yourself.? The savings in CP overhead by avoiding these tasks is small but it is not nothing.
NOTRAN and STB? (STBYPASS) current settings will show in the results of a CP Q SET command issued by that userid.
ECPS still remains the number one benefit to VM performance when running guest operating systems (and even when you are not running a guest OS).
Regards,
Bob
