BUSY and QUEUE FULL status questions

Jeff Schroeder jeffrey.schroeder at st.com
Wed Jun 9 17:39:27 PDT 1999

* From the T10 Reflector (t10 at symbios.com), posted by:
* Jeff Schroeder <jeffrey.schroeder at st.com>
I am looking for some clarification of BUSY and QUEUE FULL (TASK SET
FULL) status. It seems that both mean essentially the same thing to the
initiator, which is, "I can't accept this command right now. Please try
again later." QUEUE FULL seems almost to be the same as BUSY, but with a
specific reason for not accepting the command.

So, my question is whether initiators have different recovery actions
for these two status, or if they treat them the same. If an initiator
receives a QUEUE FULL status, will it wait for another command to
complete before retrying the rejected command, or will it retry anyway,
just as it would for BUSY? I guess I'm looking for information from
people who have implemented SCSI initiators on how they handle this.

Is it permissible to return QUEUE FULL status if the target does not
support tagged queueing?

Also, is it permissible to return either of these status without
performing the command phase? SCSI-2 doesn't really say, but the SCSI
Interlocked Protocol seems to indicate that it is not permissible.

Jeff Schroeder
TPA Americas
STMicroelectronics, Inc., San Jose, CA
Email: jeffrey.schroeder at st.com  Phone: 408-487-3965 Fax: 408-441-8470
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