$!
    $!      Project: SCSI
    $!      Project Leader:         Glenn Everhart
    $!      Development Stream:     Gryphon
    $!      Checkin Type:           Bugfix
    $!      Problem Symptom:        Devices appear offline
    $!
    $!      Diagnosis:
    $!		A number of customers have complained of non-Digital disks
    $!		which cannot be accessed using DKdriver due to "invalid
    $!		mode sense" errors. These occur because the current driver
    $!		is very picky about certain error recovery parameters
    $!		which must be set. In fact, no one knows why they need
    $!		to be set, and experiments indicate that they are not
    $!		in fact needed. Some VAX experience indicates that certain
    $!		of these bits in fact must be tolerated in the opposite
    $!		sense for some Digital HS controllers to work.  Also,
    $!		WORM devices cannot be written due to explicit check.
    $!      Cure:
    $!		Change the DKdriver tables to make bits preferred instead
    $!		of required for all bits which were required except RC. For
    $!		cluster support, ensure that bits required to be present in
    $!		drives used on cluster shared SCSI busses are still required
    $!		in the new DKdriver (by adding a copy of the old table and
    $!		running the check against it, then having the cluster mount
    $!		code in DKdriver test the results of that test).
    $!		Code will then attempt to set all bits as before (and succeed
    $!		in all previously successful cases) but tolerate other
    $!		foreign devices, reducing number of customer complaints.
    $!		Also removed the code which prevented WORM disks from being
    $!		written. This had previously been removed but was erroneously
    $!		reintroduced in a subsequent edit.
    $!      (pick one)
    $!      Platforms affected:     Alpha now, VAX planned at later time
    $!
    $!      Modules: DKDRIVER
    $!
    $!      Affected Images (if feasible):
    $!		SYS$DKDRIVER.EXE
    $!      Impact/Risks:
    $!		This has no effect on anything that previously worked, and
    $!		allows no cluster access to anything new, but allows some
    $!		third party devices to be used. While these devices may
    $!		log errors, they will at least be accessible. It also will
    $!		facilitate certain firmware changes in HS controllers which
    $!		will cause them not to report all recovered errors, since
    $!		this will allow them to be used. 
    $!      How this change was Tested:
    $!		The driver was modified and built and run against several
    $!		disks on an AXP 3000-400 running the X65N Gryphon build.
    $!		SDA verified the new cluster bit was being set and cleared
    $!		correctly and extensive running with normal SCSI disks, optical
    $!		and CD disks verified no problems induced.
    $!      Associated QARs,CLDs,SPRs:
    $!		QAR from Oxford. BURNS CD requires some of these changes also.
    $!      (Optional) Comments:
    $!
    $!      (Optional) Special Build Instructions:
    $!