SAM-5 rules on ACA condition

Gerry Houlder gerry.houlder at
Wed Aug 21 07:08:02 PDT 2013

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SAM-5r14, clause 5.9 describes the rules for establishing and clearing an
ACA condition. It is pretty complete on rules for handing commands, but
doesn't say much about task management functions.
clause 5.9.5 gives rules for clearing ACA. These rules mention things that
are caused by some task manage menfunctions (i.e., logical unit reset and
I_T nexus loss) and has a rules for when CLEAR ACA task management function
has the effect of clearing an ACA, but it isn't clear how other TMFs should
be handled when an ACA condition is active.
It seems clear that TMFs from the faulting initiator should always be
accepted and processed (there is even a mode bit that says that only TMFs
may be accepted when that bit is set) but it is unclear whether a TMF (e.g.
ABORT TASK SET) should be accepted from a non-faulting initiator. There are
rules involving the TST bit that affect whether a command should be
accepted from a non-faulting initiator but it is unclear whenther these
same rules apply to accepting a TMF from a non-faulting initiator. It is
also unclear how to handle a TMF from a non-faulting initiator if the SCSI
target device is not supposed to accept it.
I would think if the target is not supposed to accept new commands from a
non-faulting initiator, then it shouldn't accept TMFs either, except for
the ones specifically described as clearing an ACA condition. Is that
correct? then if the TST bit is set in a way that permits new commands from
a non-faulting initiator to be processed, then TMFs from that initiator
should also be processed? There isn't any text in the ACA condition handing
clauses to confirm or deny those intended behaviors.

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