Just curious, since you are talking DR and I assume hotsite. Are you
IPL'ing your VM system on that hardware directly, or running it second
level under the hotsite floor system (don't know why you would do that
just speculating...)???
Alan Altmark wrote:
On Thursday, 05/04/2006 at 02:19 EST, James Melin
<[EMAIL PROTECTED]> wrote:
I just want to reconcile what the People here are saying with what the
folk on
the list say regarding what constitutes a 3rd level guest....
I'm being told by our head sysprog AND someone else with considerably
more VM
experience (he's the new guy) that in Basic mode, the DR VM system is
first Level, our VM is second level and therefore any guests running
under OUR
VM are second level.
It sounds to me like people here on the are saying that the DR VM system
is
first level, OUR VM system is second level, and the Linux Guests running
under our VM under the DR vendor VM are in fact executing third level,
and
hitting the SIE not in hardware problem.
Which is correct?
LOL. It just depends on training and local custom. Some people use the
"level" to describe levels of virtualization. There is "1st-level SIE"
(SIE1) and "2nd-level SIE" (SIE2), so some say that any operating system
which runs under the ausipices of SIE2 is a "2nd-level guest". But I
would say the majority would use "3rd level" to describe the guests of a
2nd level z/VM system.
In Basic mode, 1st level CP (CP1) uses SIE1 to dispatch the the 2nd level
CP (CP2), which uses SIE2 to run your 3rd-level guest (Guest3). Everything
is wonderful.
In LPAR mode, LPAR uses SIE1 to dispatch CP1, which uses SIE2 to dispatch
CP2, leaving leaves none for Guest3. This means that when CP2 issues the
SIE instruction, it will cause a SIE2 break on CP1. That, in turn, causes
CP1 to construct a SIE descriptor, converting CP2's view of Guest3 to that
viewed by CP1, or to simulate whatever needs to be simulated. This
process is called "Virtual SIE" (VSIE).
The itty bitty time slices and possibly small amount of resident guest
memory in CP1 real memory means that VSIE doesn't perform very well.
Are we having fun yet?
Alan Altmark
z/VM Development
IBM Endicott
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