r DIAGNOSE Code 0008 oooe 0014 0020 0024 005C IIssued by
Function IModule(s) Executes a CP command. DETAXS Gets the current time
and date.
Manipulates input spool
files. Perforas general I/O without interrupt.
Determines virtual de­
vice tYFe information.
Edits error messages. DETREX DMTCEX DfiTriGX DETSML DMTNPT D8TS8L D8'INPT DPJTAXS DHTSHL DMTNPT DMTINI DHTREX DETLAX DMTSML DHTREX Figure 3. V8/310 DIAGNOSE Instructions Issued ty the Rses Program The supervisor provides only those functions that cannot be
consistently by the tasks themselves; that is, the superviser
provides only the support necessary to control and coordinate the
execution of the tasks.
In RSCS, a task is a single program or set of subprograms that can
run concurrently and autono.ously with other such programs and subprcgrams, and which uses control functions provided by the
Supervisor.
There are two of tasks: system service tasks and line driver
tasks. The system service tasks are those that provide the system sUFport functions for the supervisor and for other tasks. The line
driver tasks are these that manage the transmission paths to remote
stations and that interact between the remote stations and the system
service tasks and the Supervisor. Each line driver task manages tbe
transmission of files to and from a single remote station.
Figures 12 and 13 in Section 2 show the communications paths tetween the supervisor, system service tasks, line driver tasks, remote
stations, and V8/310 virtual machines.
The RSCS Supervisor
The Rses supervisor is composed of a set of service routines that
provide functions for the tasks that run under them. These service
routines may be called by any task. In general, they provide four kinds
of services: • Task management • I/O management • Interrupt handling • Virtual storage management
3-8 IBM V8/310: System Logic and Problem Determination--Volume 3

Task Management
The task management service routines provide three kinds
task execution control, task synchronization, and
communicaticn.
of services:
task-to-task
Task execution control includes initiating and terminating tasks. In
general, the only task to request these services is the REX system control task, which is described below. Task execution control also
includes the dispatcher, DMTDSP, which activates task execution as secn
as that task is initiated and while the task is active.
Task synchronization comprises a mechanism by which tasks are made ready or not ready for execution. When a task requests the services cf
another task, the requestor task may suspend its execution while the
request is being processed. The synchronization mechanism that
accomplishes this consists of two routines, and DMTPST. DMTWAT causes the requestor task to temporarily halt execution. DMTPST causes
a temporarily-halted task to resume execution. For more information cn
task synchronization refer to the section "Synchronizing and Dispatching
Tasks"
There are tvo types of task-to-task communications: (1) the DMTSIG routine (ALERT) and (2) the DMTGIV and DMTAKE routines (GIVE/TAKE). The DMTSIG
task to pass asynchronous
Functionally,
instruction.
routine allows a task to immediately interrupt another
it information. The interrupted task must have an
exit routine defined to handle the interruption. DMTSIG performs a function analagous to an SVC The DMTGIV and DMTAKE routines allow tasks to exchange informaticn
buffers with other tasks. The GIVE/TAKE function provides the means fer
organized enqueuing and delivery of requests for services or informaticn from one task to another.
For more information on task-to-task communications, refer to the
section "Task-to-Task Communications" in this section. liO Management I/O management for tasks consists of the following functions: • Handling requests for I/O operations • Handling 1/0 interrupts • Starting an I/O operation • Completing an I/O request Whenever a task requests the services of the I/O manager, that task builds an I/O request table to be passed to the 110 manager. This table
consists of the following information: • A synchrcnization lock for signaling I/O completion • The address of the device on which the I/O operation is to take place • The number of SENSE bytes to be returned, when applicable • The address of the channel program to be executed RSCS Introduction 3-9