> -----Original Message----- > From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of > Post, Mark K > Sent: Wednesday, May 03, 2006 6:31 PM > To: [email protected] > Subject: Re: Creating a second zVM 5.1: Spool issue > > I'd have to disagree with your final assessment.
Well, here's my thinking: MVS systems are able to derive more value from a shared res volume because the allocation and at least some of the dataset location/management information is stored in each volume VTOC, not in an external source like the CP directory (which needs to be kept in sync across multiple CP instances). CP can't just search the VTOC to find out what's where or where it can find free space for stuff -- you need something like CSE to keep all that data coordinated in multiple places, which is not exactly trivial to do, and CSE requires a fair amount of skill in setup and maintenance. There is a similar problem in MVS to maintaining multiple catalogs and catalog indexes, but there's also a lot of code in MVS to deal with this that isn't in VM (geoplexes where the speed of light is actually noticeable make this a really *interesting* problem). Second, while you *can* share minidisks by defining them in multiple overlapping directory entries on multiple systems, most VM products have both on-disk and NSS components. Again, without shared spool to get to the NSSes (which again requires CSE), you don't gain as much benefit as you do from having concatenated LPA lists that reference a system-specific volume in front of a common res or "library" shared volume. Note that I didn't say there is *no value* in a shared res volume -- I don't disagree that it's a possibly useful technique -- it's just a lot more work *on VM* to make it useful for a relatively small gain in function, and the overhead to get it working in a maintainable way is substantially larger than the benefits. David Boyes Sine Nomine Associates ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
