X3T9.2/91-76
                                                     May 13, 1991

To:      John Lohmeyer, Chairman X3T9.2


From:    Peter T. Dougherty
         Unisys Corporation
         25725 Jeronimo Rd.
         Mission Viejo, Ca 92691


Subject: LUNTAR, LUNTRN Bits, And Target Routine Functions




In section 5.6.7, of SCSI 2 Specification, draft 10c, page 5-23, 
the statement that, "Only the INQUIRY and REQUEST SENSE commands 
are valid for target routines" (LUNTAR bit =1) came as a 
surprise.   I had previously thought that the intent of the 
LUNTAR bit was to allow for manipulation of device control 
functions (or target routines) and not simply limited to the 
execution of INQUIRY and REQUEST SENSE commands.  


Limiting the allowable Target Routine commands to the INQUIRY and 
REQUEST SENSE commands will pose difficulty for future software 
implementations of "bridge type" controllers (i.e. Storage Array 
Controllers).  We envision "bridge controllers" consisting of 
front-end SCSI channels providing host attach, with back-end SCSI 
channels for storage device attachment.   The SCSI storage 
devices on the back-end of the controller would be addressed as 
Logical Units behind the control unit.  In these configurations, 
the capability to communicate to a control, or Target Routine 
(both in the bridge controller and the Logical Units) is 
necessary for the downloading of micro-code as well as other 
diagnostic type functions.

I propose that the appropriate sections be modified to include, 
as a minimum, the capability of Target Routines to accept the 
SEND DIAGNOSTIC and RECEIVE DIAGNOSTIC RESULTS commands in 
addition to the INQUIRY and REQUEST SENSE commands.