Seagate Ultra 320 - Manual (Page 18)

4 Parallel SCSI Interface Product Manual, Rev. A
Figure 2. SCSI client-server model
1.2.1 Glossary
aborted command—A SCSI command that has been ended by aborting the task created to execute it.
ACA—Auto Contingent Allegiance (see below).
additional sense code—a combination of the ADDITIONAL SENSE CODE and ADDITONAL SENSE CODE
QUALIFIER in the sense data (see SPC-4)
application client—An object that is the source of SCSI commands. An object in this sense is not a tangible
piece of hardware, but may be a single numeric parameter, such as a logical unit number, or a complex entity
that performs a set of operations or services on behalf of another object (see ANSI SAM-4, T10/1683-D).
asynchronous event notification—A procedure used by targets to notify initiators of events that occur when
a pending task does not exist for that initiator.
asynchronous transfer—An information transfer that uses the REQ/ACK handshake with an offset of zero.
auto contingent allegiance (ACA)—One of the conditions of a task set following the return of a CHECK
CONDITION status. See Section 4.4.2.
blocked task state—The state of a task that is prevented from completing due to an ACA condition.
blocking boundary—A task set boundary denoting a set of conditions that inhibit tasks outside the boundary
from entering the Enabled state.
byte—An 8-bit construct.
call—The act of invoking a procedure.
client-server—A relationship established between a pair of distributed objects where one (the client) requests
the other (the server) to perform some operation or unit of work on the client’s behalf (see SAM-4).
client—An object that requests a service from a server.
command—A request describing a unit of work to be performed by a device server.
Application
Client
Initiator
Task
Manager
Device
Server
Logical
Unit
Target
Device Service Request
Device Service Response
Task Management Request
Task Management Response