Seagate SCSI Interface Product Manual page 21

SCSI Interface Product Manual, Rev. J 7
service delivery port—A device-resident interface used by the application client, device server or task man-
ager to enter and retrieve requests and responses from the service delivery subsystem. Synonymous with
"port."
service delivery subsystem—That part of a SCSI I/O system which transmits service requests to a logical
unit or target and returns logical unit or target responses to an initiator.
service delivery transaction—A request or response sent through the service delivery subsystem.
signal—(n) A detectable asynchronous event possibly accompanied by descriptive data and parameters.
(v) The act of generating such an event.
source device—The SCSI device from which a service delivery transaction originates. See destination device.
subsystem—An element in a hierarchically partitioned system which interacts directly only with elements in
the next higher division or the next lower division of that system.
suspended information—Information stored within a logical unit that is not available to any pending tasks.
target—A SCSI device which receives SCSI commands and directs such commands to one or more logical
units for execution.
task—An object within the logical unit representing the work associated with a command or group of linked
commands. "Work" includes establishing an IT nexus, ITL nexus, ITLQ nexus and all of the other processes
associated with the execution of a command by a Logical Unit. Refer to the definitions of "object" in this glos-
sary. See also ANSI SAM-2, T10/1157-D, Section 4.9.
task abort event—An event or condition indicating that the task has been aborted by means of a task man-
agement function.
task address—An initiator identifies a task to a target using a Task Address. The Task Address object repre-
sents either a Tagged Task Address or an Untagged Task Address without regard for the tagged or untagged
nature of the Task. A Tagged Task Address is composed of a Logical Unit Identifier and a Tag. An Untagged
Task Address is composed of a Logical Unit Identifier.
task completion event—An event or condition indicating that the task has ended with a service response of
Task Complete.
task ended event—An event or condition indicating that the task has completed or aborted.
task management function—A task manager service which can be invoked by an application client to affect
the execution of one or more tasks.
task management request—A request submitted by an application client, invoking a task management func-
tion to be executed by a task manager.
task management response—The response returned to an application client by a task manager on comple-
tion of a task management request.
task manager—A server within the target which executes task management functions.
task set—A group of tasks within a target device, whose interaction is dependent on the queuing and auto
contingent allegiance rules of Section 4.6.1.
task slot—Resources within the logical unit that may be used to contain a task.
task tags—A Tag is a field containing up to 64 bits that is a component of a Tagged Task Identifier. An initiator
assigns tag values in each Tagged Task Identifier in a way that ensures that the identifier uniqueness require-
ments stated in ANSI SAM-2, T10/1157-D, Section 4.9 are met.
third-party command—A SCSI command which requires a logical unit within the target device to assume the
initiator role and send a SCSI command to a target device.
transaction—A cooperative interaction between two objects, involving the exchange of information or the exe-
cution of some service by one object on behalf of the other.
unconfirmed protocol service—A service available at the protocol service interface, which does not result in
a completion confirmation.