Introduction to RSCS The Remote Spooling Communications Subsystem (RSCSj, a component of VM/370, provides telecommunication facilities for the transmission of
bulk files between VM/370 users and remote stations. RSCS is a single
purpose operating system for a virtual machine, dedicated to the
management of files spooled to it by VM/370 users or transmitted to it
by remote stations via communication lines. Remote stations can submit
files to a VM/370 user or CMS Batch Facility for processing and receive
printer and punch output in return,. VM/370 users can submit job streams
to a remote HASP- or ASP-type batch processor. Remote stations can send
printer and punch files to other remote stations.
Locations and Links Under RSCS, all remote locations as well as the local RSCS virtual
machine are assigned a one-to eight-character alphameric location
identification. The transmission path between the RSCS virtual machine
and any single remote station is defined as a link. A link has certain
attributes that make up a link definition and these attributes are
assigned at system generation time or dynamically via the RSCS DEFINE
command. A link definition consists of a linkid (the location
identifier of the remote station), the type of remote station, the line
address to be used for transmission, the class of files to be processed,
and other information unique to the link. RSCS maintains a table of link
definitions (link table) in the module DMTSYS. A maximum of 64 links may
be defined of which any 16 may be active at anyone time.
Remote Stations
A remote station, in the context of RSCS, is any terminal or system on the other end of the link from the RSCS virtual machine. The RSCS virtual machine is also referred to as the local RSCS station. RSCS supports two general types of I/O configurations used as remote
stations.
Nonprogrammable remote terminals, such as the IBM 2780, are I/O configurations where the line protocol necessary for them to function as
remote stations is provided by the hardware. These devices are managed
by the Nonprogrammable Terminal (NPT) line driver of RSCS. Programmable remote stations, such as the IBM System/3 and System/360, are IBM processing systems with attached binary synchronous
communications adapters. These systems must be programmed to provide a MULTI-LEAVING line protocol necessary for their devices to function as
remote stations. For a detailed description of see
"Appendix B: MULTI-LEAVING." This programming support is provided by a
Remote Terminal Processor (RTP) program generated according to HASP workstation protocol and tailored to the system's hardware
configuration. Certain programmable remote stations like the System/3
can only be programmed to function as remote terminals. Others, like the System/360 and System/370, can function either as remote terminals or as
host batch systems using RSCS as a remote job entry workstation. Both
of these types of remote stations are managed by the Spool MULTI-LEAVING (SML) line driver of RSCS. Part 4. Remote Spooling Communications Subsystem (RSCS) 329

VM/370 Spool System Interface RSCS uses the V8/370 spool system to interface with VM/370 users. When a user generates a file to be transmitted to a remote location
by RSCS, he must comply with two requirements. The file must be spooled
to the RSCS virtual machine and the spool file tag associated with the
file must contain, as the first entry, the linkid (location identifier)
of the remote station to which the file is being transmitted. When a remote station transmits a card file to RSCS, the file must be
preceded by an ID card containing the userid of the virtual machine that
is to receive the file. RSCS punches the file on a virtual punch and
spools it to the appropriate virtual machine. If the userid is that of
the RSCS virtual machine and the ID card also contained valid tag data, RSCS will retrieve the file from the 18/370 spool system and forward it
to the remote station designated by the linkid in the tag data. RSCS Command Language
The RSCS command language provides the RSCS virtual machine operator
with the following capabilities: • Manipulate the status, transmission priority, class, and order of
files owned by the RSCS virtual machine. • Initialize, suspend, or terminate transmission of files to remote
terminals or stations. • Reposition or restart files currently being transmitted. • Send or forward messages and commands to remote terminals and
staticns. • Query file, link, or system information. • Monitor link activity for any remote location.
A summary of the RSCS commands is shown in Figure 43; for a full
description and the format of each, refer to "Appendix A: Remote Spooling" Communications Subsystem Commands" in the 1]L170 330 IBM VM/370 System Programmer's Guide