This must have either been with the old 370 lineage of CP (for which I cannot speak), or or have preceeded my involvement with the paging subsystem of the XA lineage of CP (that is, VM/XA, the XA builds of VM/ESA, and all z/VM releases). In my 20+ years as owner of the CP paging subsystem, I've never heard of a problem where paging overwrote the reserved portion of cylinder 0 (that is, cylinder 0, track 0). This would include spool use as well (for which the paging subsystem handles the DASD I/O). The fact that you're referring to a real paging drum does kind of date it back to before my time, though (I remember still having to support them just as I was getting started, but they were considered quite old even then). :)
It is perfectly safe to allocate cylinder 0 for page or spool usage, though we recommend not doing so simply for administrative simplicity. The only known exposure is that cylinder 0 must not be allocated as tdisk, and ICKDSF has not allowed that for quite a while now. Bill Holder z/VM Development IBM Endicott ----- Original Message ----- > Date: Wed, 23 Jan 2008 15:13:23 -0800 > Reply-To: Linux on 390 Port <LINUX-390@VM.MARIST.EDU> > Sender: Linux on 390 Port <LINUX-390@VM.MARIST.EDU> > From: Gregory Pinkowski <[EMAIL PROTECTED]> > Subject: Re: z/VM 5.2 Absurd System shutdown - PJBR > > Many years ago, when I allocated cyl 0 as "page" > (on a real paging "drum" with fixed heads) > it caused an I/O error but no problems > (CP just saved the page to another slot) > but at the next IPL the VTOC & dummy DSCB > were lost and the pack had to be reformatted > at each IPL before it would mount. ---------------------------------------------------------------------- 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
