On Wednesday, 08/18/2010 at 04:48 EDT, Tom Huegel <tehue...@gmail.com> wrote: > What is a path group id? Where do I find it. > I see this message everytime a certain user attaches or detaches a device. > HCPDPM1281I PATH E6 TO DEVICE 3B18 NOW OFFLINE; PATH GROUP ID MISMATCH.
A path group id is a 'handle' that identifies a host to a control unit. Among other housekeeping duties, it lets a disk or tape drive know whether or not to allow an I/O operation from a particular path if there is an outstanding RESERVE on the device. Bottom line, it lets the device treat all the paths to the host as a single logical pipe. One ring to rule them all. Now, on to the bizarre behavior.... Is this a device that is defined as UNSUPPORTED? (QUERY rdev. If it says "DASD" it is supported. If it says "DEV" it isn't.) If unsupported, is it defined DPS YES or NO? (DPS indicates whether or not the device supports Set Path Group ID.) When a DPS=YES device comes online, CP will set the path group id (PGID) in the device UNLESS the device is defined as unsupported with DPS NO. If you lied to CP about DPS, and then the guest comes along and sets the PGID, that will create problems for CP since he knows the guest set the PGID (CP is ever vigilant). CP will discover that the guest has set some other PGID and that it doesn't match his own. HCP1281I is the result. Setting the PGID can only be done once per IPL unless special action is taken to reset the device, CU, or chpid. It isn't clear if CP should even be checking on a DPS=NO device. The best way to get to the bottom of this is to open a PMR. Alan Altmark z/VM Development IBM Endicott
