On Wednesday, 01/14/2009 at 11:15 EST, "Boyer, William" <[email protected]> wrote: > We are attempting to create a baseline for our z/VM system and one of the > documents we are using states that DIAG98 should not be used and I would like > to understand a little more about DIAG98.
There is no reason not to use DIAG98 for those guests that you trust. Some, like VM TCP/IP, require it. The important thing to know is that it allows the guest to bypass virtual CCW translation. All addresses are real, not virtual. That means a malfing guest can overlay CP memory. > Here is the option statement for those DDR userids: > > OPTION DEVMAINT MAINTCCW DIAG98 Remove DIAG98. DDR doesn't use it. And this ID should only be for whoever is performing dasd management. A 'normal' guest doesn't need DEVMAINT or MAINTCCW. In fact, no special OPTIONs should be used if all you want to do is copy data. Alan Altmark z/VM Development IBM Endicott
