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-----Original Message----- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Kris Buelens Sent: Tuesday, March 17, 2009 12:33 PM To: ibmvm@listserv.uark.edu Subject: Re: Setup XLINK XLINK makes it possible to protect multiple minidisks on a shared pack. XLINK checks cylinder ranges. You can test this - on VMA, use LINK userid vdev 1 M - on VMB try LINK userid vdev 1 M and this should fail, CP should tell "userid vdev not linked, R/W by VMA" Note that there are no commands to dynamically the XLINK definitions as those found in SYSTEM CONFIG, and IPL is required. You don't need to define the volumes as shared, but BEWARE: - The problem is MDC: when MDC is active for a volume, CP may find request data in storage and may no go to the disk fo satisfy an I/O. Hence is an update took place in VMA a request from VMB may read backlevel data - Turn MDC OFF for the shared volumes and you are safe (the default for disks definedd as SHARED) - or, if you know 100% sure that only one system is writing to it - leave MDC ON for the volumes on the writing system - turn MDC OFF for the volumes on all reading systems (my former customer has been working like this for years) 2009/3/17 Berry van Sleeuwen <berry.vansleeu...@xs4all.nl>: > Hello Listers, > > I am looking into XLINK. The main goal is to be able to determine if a > minidiskextent on DASD is already in R/W use on a different VM. This > way we could provide for an easy switch for linux guests from one VM to another. > > We do not setup the full CSE here. SPOOL and DIRMAINT are just for > their own VM image. > > Now I have found that I need: > - XLINK_SYSTEM_INCLUDE for every VM system. > - XLINK_VOLUME_INCLUDE for every DASD volume. > - XLINK FORMAT the DASD to enable the volume for XLINK usage. > > Do I need more? For instance, it could be that there are multiple > minidisks on one volume and that the linuxguests in question are > spread across the 4 VM images. Should the DASD be set to SHARED for > this? As I understand it linux doesn't require the disks to be SHARED but I'd like to be sure. > > Are there any other issues I should prepare for? > > TIA, > Berry. > -- Kris Buelens, IBM Belgium, VM customer support
