Performance of zOS guest.

[William Boyer]

We were offered by an IBM Business Partner to have a performance study conducted, but when they found we run the zOS under zVM they informed us that IBM stated the tools would not work.  Here is a copy of what was sent to the business partner by IBM:   No, zOSPROD1 will not know about either zOSTEST or zOSPROD2. Not only that, but RMF will not really know how much CPU it (itself) is using, nor will it have any idea what the real configuration of the machine is. I'm looking for the (now ancient) article explaining why you shouldn't trust MVS performance data when it's running as a guest, but so far I haven't found it. BTW, the V=R and I/O Assist performance enhancements for high performance guests are not available in an LPAR environment, so the instruction path length is about double that of native z/OS performance. This has always been true of guests under z/VM in an LPAR, and since all processors starting with z/890 & z/990 will be LPAR only, z/VM is dropping support for V=R and I/O assist even in a non-LPAR environment, starting with z/VM 5.1. They must know this already, I'm sure.   This seems to indicate that if we would move our zOS to it’s own LPAR that we could get better performance out of the zOS system.    QUESTION:  How much better would the zOS perform in it’s own LPAR?  Currently we seem to be CPU constrained. Can we still share the zOS DASD back to zVM in READ mode on zVM?   Note: The reason we run zOS under zVM is because in the old days we only had parallel channels and we would have needed a CTC box to connect the two LPARS.  But now with a z800 and escon all I need is a cable. (Correct?)   Thanks in advance.   William L. Boyer Senior IT Consultant / Senior Systems Programmer Business and Technology Services                             One West Pennsylvania Ave. ● Suite 700 ● Baltimore, MD 21204 Office:  410.832.8300 ext. 8419 ● Fax:  410.832.8329 www.emdeon.com/vips This message is confidential, intended only for the named recipient(s) and may contain information that is privileged or exempt from disclosure under applicable law. If you are not the intended recipient(s), you are notified that the dissemination, distribution, or copying of this message is strictly prohibited. If you receive this message in error or are not the named recipient(s), please notify the sender at either the fax address or telephone number above and delete this message. Thank you.