ch04.htm

this describes managing multivendor networks

still accessing the advanced features of the AS/400 operating system.</P>
<P><A HREF="javascript:if(confirm('http://docs.rinet.ru:8080/MuNet/ch04/04fig01.gif  \n\nThis file was not retrieved by Teleport Pro, because it was redirected to an invalid location.  You should report this problem to the site\'s webmaster.  \n\nDo you want to open it from the server?'))window.location='http://docs.rinet.ru:8080/MuNet/ch04/04fig01.gif'" tppabs="http://docs.rinet.ru:8080/MuNet/ch04/04fig01.gif"><B>FIG. 4.1</B></A> <I>IBM AS/400 Advanced 36</I></P>
<P>After a seemingly successful two-and-one-half years with the AS/400, IBM revamped
the product line and made the first major version change in the OS/400 operating
system. Announced in April 1991, the D-series AS/400 models offer dramatic improvements
in price/performance ratios, and high-end D-series models cross over into the domain
of mainframe computing power. Beyond the feature content, IBM's marketing program
behind this new lineup clearly was oriented at moving any remaining System/36 and
System/38 users over to the AS/400 architecture, as well as extending the AS/400's
reach into other midrange environments.</P>
<P>The System/3X products and the AS/400 support the 5250 terminal family as the
preferred workstation line. However, the System/36, System/38 and AS/400 all have
special provisions built into their operating systems to handle 3270-type terminals.</P>
<P>The newest incarnation of the AS/400, the AS/400 Advanced System, supports high-speed
communications and includes support for wireless LANs and an Integrated Fax Adapter.
The Advanced System now runs the powerful 64-bit RISC PowerPC AS microprocessor.
Existing applications can run unchanged on the Advanced System. The AS/400 includes
IBM's AnyNet architecture, which permits communications over several public and private
networks. It supports SNA, TCP/IP, IPX, Token ring, Ethernet, and other protocols.
Some other additions include:

<UL>
	<LI><I>Web connection for OS/400.</I> Permits the AS/400 to function as a Web server
	on the Internet, and function as a repository for images and other data.<BR>
	<BR>
	
	<LI><I>Support for high-speed communications.</I> Includes network adapters for 16/4
	Mbps token ring Ethernet II or IEEE 802.3, FDDI, and Shielded Twisted Pair Distributed
	Data Interface. In addition, the High Speed Communications Adapter can support T1/J1
	or E1 communication over Frame Relay, or point-to-point SDLC lines.
</UL>

<P>There are a number of models in the Advanced Series, including:

<UL>
	<LI><I>Model 300, 310, and 320. </I>These models include the System Power Control
	Network (SPCN) and Redundant Array of Inexpensive Disks (RAID-5) storage capability.
	All three have multiple processor options and modular designs.<BR>
	<BR>
	
	<LI><I>Model 400. </I>This high-performance machine boasts 32M of main storage and
	1.96G of DASD (Direct Access Storage Device) in the base configuration.<BR>
	<BR>
	
	<LI><I>Models 500, 510, and 530.</I> These models support higher main storage and
	DASD, and can accommodate up to 200 communications lines.<BR>
	<BR>
	
	<LI><I>Models 20S and 30S, 40S, 50S, 53S.</I> These are used primarily as departmental
	servers. Under the client/server strategy, the processing is shared between the AS/400
	and intelligent clients. With Client Access/400 (formerly PC Support), client/server
	and traditional AS/400 applications can run side by side. The AS/400 is easy to install
	in an existing SNA or TCP/IP network, and can be used to manage a distributed client/server
	network. Supports a LAN Server/400 option for high-performance file serving to connected
	PCs. Since this service is tied to the operating system, one administrator can manage
	multiple LAN services from a central location. When deployed on a client/server network,
	it can be an application server, database, communications, print, or network management
	server for OS/2, Windows, DOS, UNIX, AIX, and Macintosh workstations.<BR>
	<BR>
	
	<LI><I>Model P03.</I> This 22 pound, entry-level system has connections for up to
	16 workstations. It is available for Token Ring or Ethernet LAN configurations supporting
	16 workstations, or twinax configurations supporting 14 workstations.
</UL>

<H3><A NAME="Heading8"></A><FONT COLOR="#000077">Top-end Offerings</FONT></H3>
<P>IBM's mainframe history began with the System/360 line; the success of the System/360
line led to the development and release of the System/370 in 1970. The System/370
introduced virtual storage to the IBM mainframe lineup. Its architecture became the
foundation for the high-end 3030, 3080, and 3090 lines, as well as the lower-end
4300 and 9370 lines.</P>
<P>The 20-year dynasty of the System/370 architecture ended in 1990 when IBM introduced
its System/390 architecture. The System/390 offered dramatic improvements in performance
from improved processor technology and the use of fiber optic links for high-speed
channel communications. At the same time it made the introduction, IBM unveiled a
new family of mainframes under the name ES/9000. The ES/9000 is a broad line targeted
to replace the older 9370, 4300 and 3090 lines. When IBM released the ES/9000 line
in 1990, the initial models did not feature the improved processor technology but
did offer fiber optic channels.</P>
<P>IBM shipped more large system processors in 1995 than ever before, primarily due
to a surge in S/390 shipments. IBM was the first to adopt complementary metal oxide
semiconductor (CMOS) technology for its large commercial computers. CMOS-based machines
are less expensive to make and more efficient than the older bipolar mainframe technology.
It requires less system cooling and takes up about 75 percent less floor space compared
to the bipolar technology. The S/390's Coupling Facility can link two or more CMOS
servers to form an IBM Parallel Sysplex environment, a large system image that can
combine up to 32 servers, each running 10 CMOS microprocessors.</P>
<P>The OS/390 operating system includes products for systems management and distributed
computing. The integration of VTAM, AnyNet and TCP/IP provide added flexibility,
and enable the S/390 server to manage information across a multivendor network. OS/390
has an optional Security Server to prevent unauthorized access and ensure data integrity.</P>
<P>Multiple S/390 processors can be coupled as a single system, with data sharing
and workload balancing. This method ensures a high uptime because there is no single
point of failure.</P>
<P>Efficient backup is facilitated through its massive data storage capability, and
users can dynamically add storage and processing without having to shut down the
server. Print jobs can be distributed from NetWare LANs to S/390 printers, so the
host system can access attached LAN printer resources.</P>
<P>IBM first started experimenting with CMOS in its laboratory in Germany in 1983
and first deployed it in its S/370 air-cooled mainframes in 1986. In 1990, CMOS technology
broke into the ES/9000 line. In 1994, IBM introduced its Parallel Enterprise Servers,
Parallel Transaction Servers, and Parallel Query Servers--all based on the CMOS technology.
Initially, CMOS technology complemented bipolar technology in the entry-level and
midrange arena, and it later moved to the high-end mainframe market. The older bipolar
technology had been used for more than 25 years; CMOS can either replace or coexist
with bipolar technology. CMOS uses far fewer parts than bipolar technology, which
lowers the cost of computing. The S/390 CMOS microprocessors are compatible with
existing systems and use up to 97 percent less energy--about the amount of electricity
used by a household refrigerator. CMOS is more reliable than bipolar--the S/390 Parallel
Enterprise Server, for example, has a failure rate of less than once every 20 years.
Also, unlike the older machines, no raised floors are required, and it uses significantly
less floor space.</P>
<P>The three operating systems most prevalent on the IBM mainframes are the following:

<UL>
	<LI><I>Virtual Storage Extended (DOS/VSE).</I> The oldest of the three operating
	systems, DOS/VSE is most often found on 4300 Series machines. DOS/VSE supports a
	suite of subsystems similar to those of MVS.<BR>
	<BR>
	
	<LI><I>Multiple Virtual Storage (MVS). </I>Usually found in business environments
	at the top end of the line. MVS is a direct descendent of the OS/VS2 originally released
	with the System/370. The popularity of MVS stems primarily from its suitability for
	running business applications.<BR>
	<BR>
	
	<LI><I>Virtual Machine (VM).</I> VM is unique in its capability to host other operating
	systems (thus, MVS can run underneath VM).
</UL>

<P>Each operating system has, in turn, its own set of variations. For example, MVS/Extended
System Architecture (MVS/ESA) is different from MVS/Extended Architecture (MVS/XA)
and both are, in turn, quite different from MVS/System Products (MVS/SP). The differences
in the versions rest in the capacities of the virtual storage environments they can
manage and therefore the size and number of programs they can run. The bottom line
is that two machines running MVS might not be equivalent.</P>
<P>Both VSE and MVS share the same basic operating philosophy and architecture (see
Figure 4.2).</P>
<P><A HREF="javascript:if(confirm('http://docs.rinet.ru:8080/MuNet/ch04/04fig02.gif  \n\nThis file was not retrieved by Teleport Pro, because it was redirected to an invalid location.  You should report this problem to the site\'s webmaster.  \n\nDo you want to open it from the server?'))window.location='http://docs.rinet.ru:8080/MuNet/ch04/04fig02.gif'" tppabs="http://docs.rinet.ru:8080/MuNet/ch04/04fig02.gif"><B>FIG. 4.2</B></A> <I>Traditional IBM O/S Environment</I></P>
<P>Running underneath the operating system are the following major subsystems:

<UL>
	<LI><I>Virtual Telecommunications Access Method (VTAM).</I> VTAM controls the flow
	of information from the terminal network to the programs. It also plays a major role
	in sites that use IBM's Systems Network Architecture (SNA). The packages that existed
	before VTAM and provided similar functions include Basic Telecommunications Access
	Method (BTAM), Remote Telecommunications Access Method (RTAM) and Telecommunications
	Access Method (TCAM). IBM is planning to add TCP/IP features to VTAM, enabling it
	to control multivendor traffic.<BR>
	<BR>
	
	<LI><I>Job Entry System (JES). </I>JES is responsible for the batch environment of
	the mainframe. It processes jobs submitted from local terminals or Remote Job Entry
	(RJE) workstations (specialized devices that have their own input and output capabilities).
	For example, JES can be used to receive the day's transactions from a remote bank,
	update the information on the central files, and then send a printed report of the
	activities back to the remote bank. In MVS environments, JES might be known as JES2
	or JES3 (for Releases 2 and 3). Under VSE, the job environment is handled by Priority
	Output Writers, Executions Processors and Input Readers (POWER). Other memorable
	implementations of job-handling packages include Attached Support Processor (ASP)
	and Houston Automatic Spooling Program (HASP).<BR>
	<BR>
	
	<LI><I>Time Sharing Option (TSO).</I> TSO provides an interface to terminals to enable
	program development and data file management. TSO is one of the most widely recognized
	ways of interfacing with a mainframe. Furthermore, within TSO is a menu-oriented
	utility named Interactive System Productivity Facility (ISPF) that provides a simple
	and easy- to-understand way of accessing TSO functions. Also note that TSO is capable
	of submitting jobs to the JES and monitoring their progress.<BR>
	<BR>
	
	<LI><I>Customer Information Control System (CICS). </I>CICS implements transaction-based
	routing between the terminal network and the application programs. Essentially, CICS
	receives input from terminal users and then decides which application program is
	responsible for processing each user's transaction. Once determined, CICS delivers
	the transaction to the program. A program must be written specifically to run under
	CICS. CICS has become a de facto industry standard, and because several vendors write
	applications to CICS, it can be used to share information with non-IBM systems.
</UL>

<P>The VM operating system, on the other hand, carves the mainframe into multiple,
virtual machines. Each user sees his or her own virtual machine and, more important,
virtual machines can support other operating systems, such as VSE and MVS (see Figure
4.3).</P>
<P><A HREF="javascript:if(confirm('http://docs.rinet.ru:8080/MuNet/ch04/04fig03.gif  \n\nThis file was not retrieved by Teleport Pro, because it was redirected to an invalid location.  You should report this problem to the site\'s webmaster.  \n\nDo you want to open it from the server?'))window.location='http://docs.rinet.ru:8080/MuNet/ch04/04fig03.gif'" tppabs="http://docs.rinet.ru:8080/MuNet/ch04/04fig03.gif"><B>FIG. 4.3</B></A> <I>IBM VM Environment</I> The subsystems
that work under VM include:

<UL>
	<LI><I>Control Program (CP). </I>CP is a central management facility for system resources.<BR>
	<BR>
	
	<LI><I>Conversational Monitor System (CMS).</I> CMS provides the communications between
	the user and CP. CMS is responsible for managing a user's virtual machine (or hosting
	another operating system). Multiple copies of CMS facilitate multiple virtual machines.<BR>
	<BR>
	
	<LI><I>Group Control System (GCS).</I> GCS is similar to CMS in that it is a virtual
	machine supervisor. GCS is used normally to host SNA-oriented subsystems, such as
	the Advanced Communications Function for VTAM (ACF/VTAM). This is the preferred methodology
	for implementing SNA in VM environments.<BR>