Save Data Pointer questions
Koller, James F TR
JFK1 at trpo2.tr.unisys.com
Thu Mar 6 13:26:00 PST 1997
* From the SCSI Reflector (scsi at symbios.com), posted by:
* "Koller, James F TR" <JFK1 at trpo2.tr.unisys.com>
*
I am working on a multi-processing platform that interfaces to a mainframe
host as a SCSI target device. I use the Save Data Pointer - Disconnect
message-in sequence to allow target disconnects on Read commands. When it
occurs, the disconnect sequence immediately follows the command phase in
which the Read is issued. The target follows with a reselection to complete
the command when data is available. There is never more than one of these
disconnect-reselect pairs per Read command.
My questions involve the need for a Save Data Pointer message. Our
proprietary SCSI host adapter apparently does not require it in the manner
that I do disconnects. A commodity host adapter I have recently interfaced
to also does not require it. In the latter case, however, the Save Data
Pointer actually has an occasional adverse effect and is therefore
undesirable.
Does the industry standard not require a Save Data Pointer message in the
way that I use it (i.e. sent once before any data is transferred) ?
How can I be sure that, if I omit the Save Data Pointer message, no other
commodity host adapters I try will have problems?
TIA,
Jim Koller
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