VM370 System Programmers Guide (Rel6)
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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