Database Reference
In-Depth Information
5.
Simplified systems management
: The N-tier architecture is useful in reducing the effort of
systems management especially of the software on client machines, particularly for large
enterprises that may have tens of thousands of client machines or even for enterprises that
have multilocated and decentralized IT/IS operations. For instance, for conventional client/
server systems, the plan for deploying a new version of any application would immediately
run into a difficulty of choosing between
a. Changing the entire installed base of clients in a single massive effort, during which the
normal operations come to a complete standstill
b. Undergoing a long and expensive but more regulated phase-in of the new software, dur-
ing which IT/IS is required to support multiple and mutually incompatible versions of
the server and client codes; and, above all, the new application is available to only a part
of the target user base
N-tier architecture by reason of its software-on-demand paradigm reduces the need for physical
updates of the client machines considerably; in many of these cases, the updates can be distributed
through the HTTP and a Web browser or through separately available automatic application distri-
bution systems. But in the case of applications with zero-footprint clients, like SAP, this need is com-
pletely eliminated. Moreover, as the majority of the code resides in the business logic, middleware,
and data layers that are typically deployed on centralized, back-end servers supported by professional
staff, the updates and enhancements to these layers are relatively painless.
10.1.2.2 Limits of the N-Tier Architecture
While the N-tier architectures deliver all the advantages associated with distributed systems, they
also have a downside. The N-tier systems are workable only because of a network-based data bus
for communications between the various tiers.
Such a communications layer will have the following adverse effects:
◾
Add to the latency of the system and degrade overall performance.
◾
Libraries of software components (and classes) required for interfacing with the data bus will
typically increase the size of the application.
However, the system architects usually take these problems into account at the time of planning
and designing the overall enterprise infrastructure and architecture. And in the event that these
problems become noticeable (because of dramatic increase in business and transaction volumes) or
foreseeable (because of envisaged M&A activities, split or divesting activities, etc.), the enterprise
architecture is revisited in its entirety.
10.1.3 Enterprise Architecture
Large corporations that have already invested vast sums of money in the existing enterprise appli-
cations, in infrastructure, in hardware, and employees cannot change overnight. Moreover, the
software skills and techniques that are essential for Web-based applications development are dif-
ferent from those prevalent in most of the companies. In this subsection, we will briefly examine
why a successful enterprises should be based on enterprise component architecture as embodied in
Enterprises Services Architecture starting with the mySAP ERP applications.
