Re: VM directory entry for shared DASD

[Shiminsky, Gary - OIT]

Title: RE: VM directory entry for shared DASD

I hope this helps   From the z/VM 5.2  Migration Guide   4.3.1 Reserve/Release Considerations for VSE    z/VM supports virtual reserve/release for minidisks that are not a full pack. Therefore, the cross-system communication (also called the "lock file") volume does not have to be defined as a full pack.   MDISK statements for all DASD you want to mount to VSE as shared (in other words, you want to use the S operand of the IPL ADD statement) must include the V suffix on the link mode. That is, the link mode must be MWV. If this is not done, VSE issues MSG 0I23I for the minidisks that do not have link mode MWV on their MDISK statements.   Specifying MWV does not result in any additional overhead because z/VM does not do a reserve/release to any pack unless the guest asks it to. VSE only does a reserve/release to the cross-system communication file (the "lock file") after IPL.   Note that if the cross-system communication file (the "lock file") is shared by more than one CPU, SHARED must be YES on the RDEVICE statement in the system configuration file. Also, for sharing a volume concurrently between real and virtual machines, the volume must be defined as a full-pack minidisk.   Note: z/VM supports virtual reserve/release for the virtual disks in storage function. Virtual disks in storage are temporary FBA minidisks simulated in system storage rather than mapped to real DASD. Therefore, a virtual disk in storage may be faster than other minidisks because it avoids the overhead of I/O operations. VSE guests may benefit from this function by using a virtual disk in storage instead of a permanent minidisk to store label information areas and the cross-system communication file (the "lock file"). The virtual disk in storage function may be used by a guest running any supported version or release of VSE.     0I23I      DASD ON cuu NOT PHYSICALLY SHARABLE                                                                                                                         Explanation:  An ADD command with the SHR option was given for                the disk volume at the indicated address. This disk volume is                 attached to a control unit that does not support RESERVE/RELEASE              commands.                                                                                                                                                   System Action:  For data integrity reasons the SHR option is not              reset. The system continues processing.                                                                                                                      Programmer Response:  If the message occurred during system                   start-up by ASI, you may have to correct the applicable IPL proce-            dure to avoid this message in the future.                                                                                                                   Operator Response:  Report this message to your programmer.      Gary Gary L. Shiminsky "It's What I Do!" Wormhole Xtreme Systems & Communications Sciences, Inc At TSG, OIT Services Data Center State of New Hampshire