OS/360 used the
Interval Timer feature for providing time of day and for triggering time-dependent events. The support for
S/370 made limited use of new timing facilities, but retained a dependency on the
Interval Timer. SVS uses the
TOD Clock,
Clock Comparator and
CPU Timer exclusively. OS/360 loads error recovery and transient SVC routines from
SYS1.SVCLIB into small
transient areas. SVS loads these routine from
SYS1.LPALIB into the
Pageable Link Pack Area (PLPA) during an IPL with the Create LPA (
CLPA) option; there are no transient areas. In the wake of the
Applied Data Research lawsuit IBM decided to
develop chargeable versions of several applications, mostly language processors, although it's not clear whether the lawsuit was actually the deciding factor. As a result, SVS does not include a
sort/merge program or any language processor other than the new Assembler (XF) (replacing Assembler (F)) which is required for the
system generation process.
Authorized Program Facility (APF) is a new facility that limited use of certain dangerous services to programs that are
authorized, that is link edited with
AC(1) and were loaded from the link list, LPA, or
SYS1.SVCLIB. In
MVS IBM enhanced the facility to allow the installation to designate additional data sets as authorized. Because the Reader/Interpreter in SVS runs in pageable storage, there is much less benefit to the Automatic SYSIN Batching (ASB) Reader, and SVS does not include it. OS/360 has a facility called
Direct SYSOUT (DSO) whereby specific output classes can be diverted to data sets on tape instead of normal
SPOOL datasets. As
DASD prices dropped, the facility dropped from use, and SVS does not provide it. OS/360 provides limited interactive facilities in
Conversational Remote Job Entry (CRJE),
Graphic Job Processing (GJP),
Interactive Terminal Facility (ITF) and
Satellite Graphic Job Processing (SGJP) prior to the
Time Sharing Option (TSO), but IBM did not carry those forward to SVS. TSO continues to provide equivalent facilities, except that it does not support use of a
2250 as a terminal. Use of 2250 from a batch job using
Graphics Access Method (GAM) and
Graphics Subroutine Package (GSP) remains supported. OS/360 includes a batch debugging facility named
TESTRAN; it is clumsier than the equivalent facility in
IBSYS/IBJOB, and was not used much. With the advent of TSO
TESTRAN became even less relevant, and SVS does not include it.
Dynamic Support System (DSS) was a new OS/VS debugging facility for system software. It remained available until Selectable Unit 64 and MVS/System Extensions Release 2. The storage key facility of
System/360 and
System/370 keeps track of when a page frame has been modified. The
Machine Check Handler (MCH) in SVS can correct a parity or ECC error in an unmodified page by unassigning the damaged page frame and marking the page table entry to cause a pagein operation into a newly assigned page table. This replaces the special handling of refreshable transient
SVC routines in OS/360. SVS expands the size of the
Error Recovery Procedure (ERP) transient area. None of the processors on which SVS runs have an equivalent to the 2361 Large Core Storage (LCS), and thus there is no need for Hierarchy support, which SVS does not provide. SVS also dropped support for some obsolete I/O equipment. In OS/360 load modules can be permanently loaded at
Initial Program Load (IPL) time into an area of real storage known as the
Link Pack Area (LPA). In SVS the LPA was split into three areas, each of which is searched in turn. :*The installation can specify a list of modules to be loaded into the
Fixed Link Pack Area (FLPA). These are loaded into V=R storage at IPL time. :*The installation can specify a list of load modules to be loaded into the
Modified Link Pack Area (MLPA) at IPL time. These modules are subject to normal paging. :*SVS uses a dedicated paging data set to back up the
Permanent Link Pack Area (PLPA). In a normal IPL, SVS will simply allow modules in the existing PLPA paging data set to be paged in at need, but the operator can specify the CLPA option to load all of the load modules from
SYS1.LPALIB into the PLPA and write the new PLPA into the PLPA paging data set. OS/360 has support for a multiprocessor version of the 360/65. SVS provide no equivalent support; customers wanting to run a multiprocessor System/370 have to use
MVS. OS/360 introduced
Telecommunications Access Method (TCAM) as the successor to
Queued Telecommunications Access Method (QTAM). SVS does not include QTAM. SVS does not include
Remote Job Entry (RJE). However, ASP and HASP provide comparable facilities. Because of the larger (16 MiB) address space that SVS provides, there is less external fragmentation than in MVT, and Rollin/Rollout would provide less of a benefit. SVS does not include it. In OS/360, transient
SVC routines are loaded into 1 KiB areas known as SVC Transient Areas, and a considerable amount of code is required to manage them. In SVS, all SVC routines are preloaded into virtual storage and there are no SVC Transient Areas. While SVS retains the SPOOL support of
OS/360, most shops used ASP or HASP, the precursors of JES3 and JES2, respectively. ==Storage Management==