Hi, I spent three days on this and had some thoughts----but don't know whether they're right. What I have is just a MVS system running on pc and I never had the chance even to see the real big machine. So it's really hard for me to understand some hardware parts of mainframe. 1. Init & Tuning book says there're three mount attributes: permanently resident, reserved and removable. Some volumes such as sysres pack will be definitely treated as 'resident' by NIP and the others will have the attribute specified in VATLSTXX. If not specified in VATLSTXX, the default attribute is 'removable'. However, I found out it's not true at least on my z/os system. I have some user volumes and there are no entries in VATLSTXX for them. As manual says, they should have the 'removable' attribute. But actually it's 'resident'(I use 'd u,dasd,online' command to know that) And suprisingly these user volumes can be varied offline even though they hold the 'resident' attribute. But for SYSRES volumes, I still will get 'invalid unit' message when I try to vary them offline.
2. Then I got some hints from redbook 'os390 and z/os new users cookbook' and one article from xephon : http://www.xephon.com/arcinframe.php//m018a07 So nowadays mainframe DASD volumes are pratically non-removable and as redbook says mount attributes are not very relevant. Here are some conclusions I made: 1. 'UNLOAD' command doesn't make sense for DASD volumes any longer since they actually cannot be dismounted. I also tried to issue UNLOAD command against one user volume on my sytem and everytime I got 'unit invalid' message. 2. What we can do is to vary that volume offline. I successfully did that with the volume mentioned above. 3. Mount attribute is irrelevant in most cases except for those treated as 'resident' by NIP(SYSRES volume, page volume, linklib volume..etc.) For them, you cannot vary them offline. 4. Unlike 'UNLOAD' command, 'MOUNT' command can still be useful. When a volume is varied online, it'll get its USE attribue from VATLSTXX(private, public or storage). Then we can use 'MOUNT' command to change its USE attribute(I tried this on my system) if you really want to change it. Are there any errors? Any inputs will be appreciated :) Thanks. -- Best Regards, Johnny Luo ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
