  SCSI-related System Hang? 
 The Question is:
 
I'm trying to do an image of two disk drives, dka0 and dka100.  The image of
dka0 works fine, but the process when copying dka100 stalls when it
encounters a particular file that is 245,000 blocks in size.  The tape drive
stops writing and will sit there
for hours until the Vax is reset.  Normally this file takes about 5 minutes
or so to copy.
 
I've used different tapes and different tape drives: Exabyte 8mm and a 4mm
DAT.  Same problem.  I've run the analyze utility to check for dka100
errors: none.  No tape drive errors either.  The tape and disk drives
operate normally when VMS is booted and
running.  DKA100 is a 2 Gbyte Quantum Fireball SCSI drive, DKA0 is 1 Gbyte
Seagate ST51080N.
 
The backup utility is version 7.1.  We did not have this problem booting the
utility from a 5.5.2 VMS tape when the system had VMS 6.1 on it.  We did not
have this problem with a smaller dka100 drive (the drive was recently
replaced because the original c
ratered.)
 
I have 12 years VMS experience and have consulted with many other experts
who are baffled.
 
Help me Mr. Wizard
 
Bob Found
Spartan Controls Ltd, Calgary
A representative of Fisher-Rosemount Systems, Austin, TX.
 
 
 The Answer is:
 
  It is not clear if this is an OpenVMS problem, a SCSI disk problem,
  a SCSI tape problem, or a SCSI bus problem -- the OpenVMS Wizard would
  first suggest trying this same test on a supported disk drive, as well
  as checking for the appropriate bus termination and minimal bus length.
 
  Please contact the Compaq Customer Support Center.
 
  Expect to be asked details of the particular system involved, as well
  as the command(s) used, as well for any relevent contents found in the
  system error log, as well as for tests with other (supported) SCSI disks
  and tapes.  The Customer Support Center will also likely want to see the
  contents of a system dump forced during the reported hang -- if this is
  even found to be possible during the reported system hang.
 
