The data areas discussed below give a brief functional overview of each data area and its relationship to other data areas in the system.
This is not meant to be a comprehensive description of the RSCS data
areas. Rather, it is meant as an introduction to the types of data used by RSCS in Ferforming its various functions. SVECTORS: SUPERVISOR CONTROL QUEUES AND SUPERVISOR ROUTINE ADDRESSES The SVECTORS DSECT contains: 0 The PSi the last task dispatched The RSCS System Save area The task ID and task element address for the last task dispatched pointers tc the Rses supervisor subqueues Entry addresses for all supervisor service routines
This data area is updated dynamically as tasks execute and is used by RSCS to monitor the execution status of the system. RSCS SUPERVISOR QUEUE ELEMENTS All supervisor status information pertaining to tasks and task requests
is maintained in Supervisor storage defined by the SVECTORS DSECT. There are various queues defined in this DSECT, each pertaining to a
particular Supervisor function, and composed cf elements of similar
format. The heads of these queues are defined in a portion of SVECTOES from FREEQ through GIVEQ. The DSECTS defining the elements chained cn
these queues are: FREEE, TASKE, IOE, ASINE, and GIVEE. MAINMAP: STORAGE AVAILABLE TO RSCS PROGRAMS AND TASKS The MAINMAP DSECT is a grid of a fixed number of bytes
each of which
represents a page of virtual storage. When a task (or the Supervisor) requests storage, the byte is filled with the TASKIt (generated by the Supervisor) of the requestor, thus marking the storage page as taken by that task. When a page is free, its map entry is cleared to zero by the
task owning the storage.
TAREA: THE SAVE AREA FOR AN INTERRUPTED TASK The TAREA DSECT contains the PSi at which a task is to resume execution,
the contents of the task general registers when it was interrupted; and
the task's request synchronization lock. This area is used to maintain
the status of a task when it is interrupted by another task.
The LINKTABL DSECT describes control data associated with each link in
the system. The control data includes such information as the linkid cf
the link, the task ,name for the link's line driver (that is, the name by RSCS Introduction 3-19
which RSCS knows the task), the address of the line which is used by the link, and se on. The link table (a chain of LINKTAEL DSECTs) is built
during system generation and may be updated ty the DEFINE, DELETE, START, and DRAIN commands.
TAG: RSCS FILE DESCRIPTOR The TAG DSECT defines the attributes and status of a file being processed by RSCS. The TAG is built from information passed via the CF
TAG command (or its counterpart for remote stations) and from the CF SFool File Bleck (SFBLOK) that describes the file. RSCS REQUEST ELEMENTS Request elements are data tables built by task programs when a service is to be requested by the task.
For example, when a command is processed by tMTCMX, the command line may be formatted into ao command element, which gives the following types
of information: Length of the command element The unique code identifying the command element The linkid to which command response is to be returned Modifiers that specify options for a given command A variable length buffer field containing the command line
This command element is then passed (via D81SIG) to another task fer
processing. Other types of request elements are built to process individual
commands and messages, to create and terminate tasks, to process console I/O, and so on.
In many cases, elements are contained in a generalized control area
used when processing a system function, for example, monitoring requests
for DMTAXS module to open or close a V8/370 spool file. VM/370 DATA AREAS REFERENCED BY RSCS There are two V8/370 CP data areas referenced by RSCS when V8/370 spocl
files are processed: SFBLOK The VM/370 spool file block that contains control information
and describes attributes of a VM/370 spool file. SPLINK The data block that links pages of a VM/37C spool file buffer. RSCS Storage Requirements
Figure 7 shews the storage used by the BSCS control program and how the parts of the system (the Supervisor, the tasks, and the data areas) fit
together in storage. 3-20 IBM VM/370: System Logic and Problem Determination--Volume 3
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