But why is it not worth the effort? Is it because, with full-pack paging devices, they were never using it? IIRC, at one time, perhaps still, MVS required that paging be isolated on its own devices.
Regards, Richard Schuh -----Original Message----- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of McKown, John Sent: Tuesday, April 10, 2007 1:34 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: Time to move > -----Original Message----- > From: The IBM z/VM Operating System > [mailto:[EMAIL PROTECTED] On Behalf Of David Kreuter > Sent: Tuesday, April 10, 2007 3:22 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: Time to move > > > It's IO. A SSCH (start channel) instruction is issued with > the modify bit on. Then the program can issue a RSCH (resume > subchannel) which continues the channel program with the > initial i/o ending, allowing for an almost continuous data > feed. You can throw new CCWs (channel commands) at it for > read and write. > > While most shops no longer are concerned with physical device > geometry, what with everything stored electronically, > obviating true seeks, it is still expensive and unnecessary > to end the channel program and fire it up again. That's why > it is always recommended to keep paging "cylinders" isolated > from all others. > > All CP io uses the seldom ending channel program (paging, > spool, directory, warm, ckpt). > > Consider if you mix page and drct. Drct access will occur. > If a page RSCH in in process it will end (only one i/o at a > time san PAV!) so the drct i/o can start. Then a page is > needed for paging; the drct RSCH is ended then the page > SSCH/RSCH starts. Not good. > > David Curiously, the z/OS developers now say that SUSPEND / RESUME is not worth the effort and have removed it from their paging I/O. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology The information contained in this e-mail message may be privileged and/or confidential. It is for intended addressee(s) only. If you are not the intended recipient, you are hereby notified that any disclosure, reproduction, distribution or other use of this communication is strictly prohibited and could, in certain circumstances, be a criminal offense. If you have received this e-mail in error, please notify the sender by reply and delete this message without copying or disclosing it.
