Ian, I don't know from which operating system background you're coming, but I'm guessing it's not an IBM operating system. IBM does an amazing job of clearly documenting almost everything about their mainframe operating systems.
It may take time, but it's worth taking the time to at least skim over the complete z/VM library so that one knows what's documented even if not taking the (significant) time required for an in-depth read. Good web sites (although I still stubbornly prefer hardcopy manuals in binders) for such a scan include: http://www.elink.ibmlink.ibm.com/publications/servlet/pbi.wss?CTY=US http://www.vm.ibm.com/library/ http://www.vm.ibm.com/pubs/redbooks/ To answer your question about the access extension and search order more directly, read: "z/VM: CMS User's Guide" (SC24-6137), Chapter 5, "How File Mode Letters Are Used" (which explains extensions, and a little on search order), and "z/VM: CMS Commands and Utilities Reference" (SC24-6073), Chapter 1, "CMS Command Search Order". Even though you might access a disk as an extension of another disk (or itself), the disk may still be linked R/W. When using the "CP DEFINE MDISK" command (something best done only after very careful reading of all its implications) the defined MDISK is always defined R/W. The ACCESS command provides a good means to prevent accidental update of that defined MDISK, e.g. ACCESS 100 Q/Q --- the disk is still defined R/W, but CMS will not let you accidentally write to filemode Q (in this example). Regards, Mike Walter Hewitt Associates Any opinions expressed herein are mine alone and do not necessarily represent the opinions or policies of Hewitt Associates. "Ian S. Worthington" <[EMAIL PROTECTED]> Sent by: "The IBM z/VM Operating System" <[email protected]> 06/28/2007 10:04 AM Please respond to "The IBM z/VM Operating System" <[email protected]> To [email protected] cc Subject Re: ACCESS /extension Hmmm. That's what I was hoping for, but with EXECs. Maybe those are found differently. When my VM's available I'll test it again. Thanks, ian ... ------ Original Message ------ Received: Thu, 28 Jun 2007 03:49:07 PM BST From: Rob van der Heij <[EMAIL PROTECTED]> To: [email protected] Subject: Re: ACCESS /extension On 6/28/07, Ian S. Worthington <[EMAIL PROTECTED]> wrote: > I've never understood this, and have only used it when I wish to make a disk > r/o. I certainly does not work for making a disk appear elsewhere in the > CMS search order, which is what I would really like it to do (when I have to > squeeze a disk in where there isn't a hole). It does not affect LISTFILE for example, but it does silently take the file from the R/O extension if it does not exist yet on the disk where you asked for it. Like this (showing a file does not exist on my A disk, but can be read when J/A ) acc 100 j DMSACC724I 100 replaces J (100) DMSACP723I J (100) R/O Ready; T=0.01/0.01 10:47:39 pipe < esasys history a | count bytes | cons FPLDSR146E File "ESASYS HISTORY A1" does not exist FPLSCA003I ... Issued from stage 1 of pipeline 1 FPLSCA001I ... Running "< esasys history a" Ready(00146); T=0.01/0.01 10:47:42 acc 100 j/a DMSACC724I 100 replaces J (100) DMSACP723I J (100) R/O Ready; T=0.01/0.01 10:48:10 pipe < esasys history a | count bytes | cons 399648 Ready; T=0.01/0.01 10:48:12 The information contained in this e-mail and any accompanying documents may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient of this message, or if this message has been addressed to you in error, please immediately alert the sender by reply e-mail and then delete this message, including any attachments. Any dissemination, distribution or other use of the contents of this message by anyone other than the intended recipient is strictly prohibited.
