What is "FBAF"? I can't find that reference anywhere. On Tue, Mar 12, 2013 at 11:28 AM, Alan Altmark <[email protected]>wrote:
> On Tuesday, 03/12/2013 at 08:33 EDT, "Pavelka, Tomas" > <[email protected]> wrote: > > We have been trying to format all minidisks from Linux only and this > turned out > > to be problematic. I am looking for a solution that would let us stay in > Linux > > without having to involve CMS format for every new minidisk. Let me > first > > describe the problem: > > When there is a record on dasd that has incorrect cylinder in the count > area, > > this leads to "record not found" errors when the dasd is brought online. > Since > > the dasd needs to be online before the problem is fixed (by formatting) > the > > only way around that I can see is to preformat in CMS. > > If new minidisks are regularly formatted and destroyed, it is possible > to run > > into situation where part of the disk has the correct format and part > has the > > cylinder number in the count area wrong. > > What you have identified isn't new, and it affects all operating systems. > Any disk space that is decommissioned needs to be formatted in some way > to avoid precisely this kind of problem. If you gave z/OS a volume with a > valid label and VTOC, but the index pointed to garbage or near-garbage, > bad things would happen. If there's something that looks like a valid > label on the disk, then the OS will start looking further. At some point > in that process, the OS finds a Magic Cookie and based on that decides > that the disk has been formatted. It will *assume* that all internal > pointers on the disk are valid and consistent. > > If there is no sign of a volume label, or the label indicates the hen the > OS assumes the disk is NOT formatted and it won't read any further. > > If you're using minidisks, then you erase a decommissioned disk before you > give it to another guest. You can have DIRMAINT do it automatically by > putting DISK_CLEANUP=YES in your CONFIGxx DATADVH file. That way, if the > old cylinder 0 gets re-used as the new cylinder 0, the guest sees an empty > disk. If something other than cyl 0 get used, then the guest will see all > zeroes (no label). > > Write garbage in the middle of a SCSI LUN and watch the OS go nuts. The > biggest fear is that 'garbage' is semantically valid. Then you end up > reading random data from the disk with no I/O errors - just bad data. > > Alan Altmark > > Senior Managing z/VM and Linux Consultant > IBM System Lab Services and Training > ibm.com/systems/services/labservices > office: 607.429.3323 > mobile; 607.321.7556 > [email protected] > IBM Endicott > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- > For more information on Linux on System z, visit > http://wiki.linuxvm.org/ > ---------------------------------------------------------------------- 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 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
