I think you can say best practice is on a need to know basis. This is especially important for some industries :) You really can't say you have a security system in place if something else can get there without it going through that security system.
Does z/OS *need* to access your disk? (maybe they do if you do backups from there) Does z/VM *need* to access z/OS disks? (we have some isolated volumes that z/OS writes and z/VM reads, so yeah, but only on a very limited basis) Both Richard and Scott are correct (of course!). We do it at a gen level. That's most restrictive. And of course if you are doing it with a gen, then by LCU makes most sense or screwing up LPAR access lists becomes what easier :) You have not made mountains. They do exist :) Richards performance example is another reason. VM's i/o characteristics are shall we say "less friendly" to replication needs than z/Os is and tracking down performance problems are definitely more difficult if more than one o/s is hitting your subsystem. Marcy This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this for the addressee, you must not use, copy, disclose, or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. -----Original Message----- From: The IBM z/VM Operating System [mailto:IBMVM@LISTSERV.UARK.EDU] On Behalf Of Karl Huf Sent: Tuesday, April 05, 2011 3:44 PM To: IBMVM@LISTSERV.UARK.EDU Subject: [IBMVM] z/VM & z/OS sharing same DASD I could have sworn I had seen something about this in a presentation regarding "best practices" for configuring z/OS & z/VM LPAR's that share the same DASD subsystems but now that I need it, no joy. We have 2 (z10) CEC's, each with z/VM and z/OS LPAR's attached via FICON Directors to a pair of DS8700's. As currently configured all of the DASD is defined on common LCU's and all of the DASD is online to all systems. This makes me nervous but perhaps my fears are unfounded? My gut tells me that a better configuration would be having the VM DASD segregated onto dedicated LCU's and the rest of the MVS DASD on their own LCU's - and that the respective devices not be online to the "foreign" OS's. Due to other recent discoveries we have some DASD reconfiguration work ahead of us anyway and, if it's worthwhile, I'd like to pile on with getting the VM DASD to be isolated as part of that work - but at the moment I can't quantify to those that would do the work why. Are there good reasons or am I making mountains where there are no molehills? TIA. _______________________________________________________________________________ Karl S Huf | Senior Vice President | World Wide Technology 840 S Canal, Chicago, IL, 60607 | phone (312)630-6287 | k...@ntrs.com Please visit northerntrust.com CONFIDENTIALITY NOTICE: This communication is confidential, may be privileged and is meant only for the intended recipient. If you are not the intended recipient, please notify the sender ASAP and delete this message from your system. IRS CIRCULAR 230 NOTICE: To the extent that this message or any attachment concerns tax matters, it is not intended to be used and cannot be used by a taxpayer for the purpose of avoiding penalties that may be imposed by law. For more information about this notice, see http://www.northerntrust.com/circular230 P Please consider the environment before printing this e-mail.
