MicroVAX 3800 DSSI Issues

Peter Coghlan cctalk at beyondthepale.ie
Tue Sep 1 17:12:18 CDT 2015

> Yeah, your disk has got problems. Either an actual hardware problem or a
> corrupted file system.
> The FORCEDERROR flag usually means a hardware problem - bad disk block.  It
> means reading the disk, the checksum failed and retries did not successfully
> read the data so the disk controller has flagged the block as bad.  It looks
> like this has happened in one of the blocks for the storage bitmap that VMS
> uses in the interal file structure to maork used blocks.  Doing an
> ANALYZE /DISK /REPAIR dub0:  may fix it.  You also may have to initialize
> the disk and run a bad block checker on it.  Doing this will lose whatever
> data is on the drive though so try the ANALYZE first.

ANALYZE /DISK /REPAIR dub0: requires the disk to be mounted first and the
forced errors on the bitmap likely won't allow that.  It has a better chance of
working if the disk is backed up and restored onto a working disk, possibly an
emulated disk on simh or similar.  ANALYZE /DISK /REPAIR is also a very blunt
weapon and when combined with media errors, it could mangle the disk much worse
so it's always a good idea to try it on a copy of the original.

Peter Coghlan.

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