Basic Networking

With an object server, the Client/Server application is written as a set of communicating objects. Client object communicate with server objects using an Object Request Broker (ORB). The client invokes a method on a remote object. The ORB locates an instance of that object server class, invokes the requested method and returns the results to the client object. Server objects must provide support for concurrency and sharing. The ORB brings it all together.

With a transaction server, the client invokes remote procedures that reside on the server with an SQL database engine. These remote procedures on the server execute a group of SQL statements. The network exchange consists of a single request/reply message. The SQL statements either all succeed or fail as a unit.

User interface

Business Logic and

Shared data.

With a database server, the client passes SQL requests as messages to the database server. The results of each SQL command are returned over the network. The server uses its own processing power to find the request data instead of passing all the records back to the client and then getting it find its own data. The result is a much more efficient use of distributed processing power. It is also known as SQL engine.

Ubiquitous communications

Network OS extension

Binary large objects (BLOBs)

Global directories and Network yellow pages

Authentication and Authorization services

System management

Network time

Database and transaction services

Internet services

Object- oriented services

Triggers are special user defined actions usually in the form of stored procedures, that are automatically invoked by the server based on data related events. It can perform complex actions and can use the full power of procedural languages.

A rule is a special type of trigger that is used to perform simple checks on data.

Transparency really means hiding the network and its servers from the users and even the application programmers.

TP-Lite is simply the integration of TP Monitor functions in the database engines.

TP-Heavy are TP Monitors which supports the Client/Server architecture and allow PC to initiate some very complex multiserver transaction from the desktop.

TP lite, based on stored procedures. TP heavy, based on the TP monitors.

This new model of Client/Server consists of thin, portable, "universal" clients that talk to super fat servers. In the simplest form, a web server returns documents when clients ask for them by name. The clients and server communicate using an RPC-like protocol called HTTP.

These are fully-loaded machines which includes multiprocessors, high-speed disk arrays for interview I/O and fault tolerant features.

There is no commonly accepted definition for a TP monitor. According to Jeri Edwards' a TP Monitor is "an OS for transaction processing".

They were originally introduced to run classes of applications that could service hundreds and sometimes thousands of clients. TP Monitors provide an OS - on top of existing OS - that connects in real time these thousands of humans with a pool of shared server processes.

There is a many-to-one relationship between clients and server. Clients always initiate the dialog by requesting a service. Servers are passively awaiting for requests from clients.

The types of transparencies the NOS middle ware is expected to provide are:-

Location transparency

Namespace transparency

Logon transparency

Replication transparency

Local/Remote access transparency

Distributed time transparency

Failure transparency and

Administration transparency.

The triggers are called implicitly by database generated events, while stored procedures are called explicitly by client applications.

The grouped SQL statements are called Transactions (or) A transaction is a collection of actions embused with ACID properties.

The client

The server and

Middleware.

The client side building block runs the client side of the application.

The server side building block runs the server side of the application.

Transport stack

Network OS

Service-specific middleware.