Glossary; Figure 2. Scsi Client-Server Model - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
1157-D (SAM-3) should be well understood before reading operation descriptions in any SCSI docu-
ment. Although a Glossary of terms is provided herein, the definitions may not be adequate for some.
The SAM-3 specification gives a more detailed understanding of some of the new SCSI terminology.
Application
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).
ACA command—A command performed by a task with the ACA attribute (see Section 4.6.1).
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-2, T10/1157-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.
auto contingent allegiance—The condition of a task set following the return of a Check Condition or Com-
mand Terminated status.
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 ANSI SAM-2, T10/
1157-D).
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.
command descriptor block—A structure up to 16 bytes in length used to communicate a command from an
application client to a device server.
completed command—A command that has ended by returning a status and service response of Task Com-
plete, Linked Command Complete, or Linked Command Complete (with Flag).
completed task—A task that has ended by returning a status and service response of Task Complete. The
actual events comprising the Task Complete response are protocol specific.
Device Service Request
Client
Device Service Response
Task Management Request
Task Management Response
Initiator
Logical
Unit
Device
Server
Task
Manager
Target
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