[Info-vax] analyze/disk errors

[Paul Sture]

tadamsmar wrote:

> On Thursday, December 5, 2013 1:45:58 PM UTC-5, hb wrote:
>> On 12/05/2013 05:16 PM, tadamsmar wrote:
>> 
>> > ANAL/DISK gave me a this warning ANALDISK-W-MAPAREA on BADBLK.SYS and some other files.
>> 
>> 
>> 
>> I don't know what analyze/disk is checking and what makes it issue such
>> 
>> a "warning". If the map area is invalid or even corrupted as
>> 
>> help/message states, then you usually can not get away with copying the
>> 
>> file contents: the map area describes the disk blocks containing the
>> 
>> file data. Ask your friend backup to restore the "some other files".
>> 
>> 
>> 
>> > ... So I tried to do copy it.  Copying worked on the other files, but I got an error when I tried to copy BADBLK.SYS....
>> 
>> 
>> 
>> Besides any map area problem, that's expected or the "nature" of
>> 
>> BADBLK.SYS: it contains/maps all the disk blocks which are not
>> 
>> guaranteed to be read. Mapping is done on the disk cluster base, so
>> 
>> there may be some good and some bad blocks. As far as I know, todays
>> 
>> disks do bad block replacement so, as long as that works, there should
>> 
>> not be real bad disk blocks in that file. But BADBLK.SYS may contain
>> 
>> "the end" of the disk. Consider a disk with 1000 blocks and a cluster
>> 
>> size of 3. Then BADBLK.SYS contains/maps one cluster, that is three disk
>> 
>> blocks starting at logical block number (zero based) 999. That's all
>> 
>> normal (no ANALDISK-W-MAPAREA) and expected as well as an error when
>> 
>> trying to copy such a BADBLK.SYS.
>> 
>> 
>> 
>> > So I made an image backup and restored the image from that backup and that cleared up the warning on BADBLK.SYS.
>> 
>> 
>> 
>> Because an image backup only contains the file header of the BADBLK.SYS
>> 
>> and a new BADBLK.SYS is created by backup when it restores the image
>> 
>> backup and implicitly initializes the disk (or by an explicit init
>> 
>> command if the restore is done with the /noinitialize).
>> 
>> 
>> 
>> And now, for fun, try to copy BADBLK.SYS to NLA0:. Any error?
> There the HELP/MESSAGE on the MAPAREA error:
>
>
>  MAPAREA,  file ('file-id') 'file-name' invalid map area
>
>   Facility:     ANALDISK, Analyze/Disk_Structure Utility
>
>   Explanation:  The specified file has a corrupted map area.
>
>   User Action:  The damage can probably be repaired by copying the file to
>                 a new version and deleting the original version. It might be
>                 necessary to reconstruct the file from backup media.
>
> I just followed the instructions.
>
> A number of you seem to think that the VMS documentation is full of bull.

Popcorn anyone?
-- 
Paul Sture