Structure of RSCS Virtual Storage RSCS virtual storage is made up of
supervisor service routines
r system modules r and available free storage for
how RSCS storage is allocated.
fixed address storage
service modules# line
areas
r
driver
__ "'-: _ _ L _ _ , ... .- C1\.,.L..1.V\:: 1.C1::::>l\.::::>. Figure 44 shows Or -, 10000 r ,---------------- DMTVEC I / 270 1 I DMTKAP I I DMTCMX I 1----------------------\ DMTEXT I I DMTliGX I 1 I I DI1TSVC I I DMTCRE , I 1----------- I DMTIDK I , DMTCOM , I I 1 DMTQRQ I I DMTMSG I 1 I I DMTDSP I I DMTSYSI , 1 1---------- I DMTWAT I I DHTIHI2 , 1 , DMTPST I Free St::>rage I I I DMTASK / I / I DMTSTJ / I / I DMTASY / I I I DMTSIG I I I I DItTGIV I I I / I , DMTAKE 700001---------------- , 1---------------------1 , Third Line Driver I 10001 1 740001 , I Supervisor Queue Extension I , Second Lin' Driver I 20001 I 780001--- , I I 1 First Lin-' Dri.ver I I I ------1 I I I DMTL\x I I I 7DOOOI -------1 I Free storage I 1 DMTAXS 1 I (allocatable) I 80000 L- _____ J I I L lThe DKrSYS .odule can vary in size depending on the number of macros specified when the RSCS systea was generated. Free storage starts on the first page following the
end of DMTSYS. 2The DMTINI module is loaded at the beginning of the free storage area. After
initialization, the storage it occupied is freed and beco.es part of free storage.
Figure 44. RSCS Storage Allocation
332 IBM VM/370 System Programmer's Guide

RSCS Supervisor
The first 4K bytes of contain hardware and supervisor-defined
constants, control areas, and supervisor service routines. The first bytes of are defined by System/370 architecture and contain hardware-defined constants. This area is
initialized by the DMTINI routine at initial program load time.
The rest of DMTVEC, 112 bytes, contains supervisor-defined addresses
and constants used for dispatching, storage maPfin9, queue management,
and task management. DMTMAP: The supervisor storage area contains the main storage map and the-fIrst extent of the supervisor queue.
The main storage map is a table comprising one byte for each page in
accessible storage. Each byte displacement in the table implies an
associated main storage number.
The supervisor queue is a chain of 16-byte elements, formatted during
initialization, maintained by the DMTQRQ routine, and containing the
status information for all system tasks running or waiting to be
dispatched. The length of this chain is such that the service routines
that follow are located at the end of the page of storage. ftgy!!ng§: The rest of the supervisor contains service
routines that provide services to other system tasks, as follows: DMTEXT DMTSVC DMTIOM DMTQRQ DMTDSP DMTWAT DMTPST DMTASK DMTSTO DMTASY DMTSIG DMTGIV DMTAKE
Function Handle-external interruptions
Handle SVC interruptions
Handle I/O interrupts and requests
Manage the supervisor status queue
Dispatch eligible tasks Suspend task execution Signal completion of an event
Create and delete system service tasks
Reserve and release main storage pages
Provide asynchronous task to task exits
Interrupt a task, immediately, for an ALERT request
Enqueue a GIVE request element for another task
Process a GIVE request element
Supervisor Queue Extension
The supervisor queue extension is a chain of 16-byte elements that
provide an extension to the supervisor queue located in DMTMAP. Free Storage
This area of free storage is managed by the module. Syste. tasks
reserve and release virtual storage in full page increments as required. Part 4. Remote Spooling Communications Subsystem (RSCS) 333