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.

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...

If the bulk of the application runs on the Client side, then it is Fat clients. It is used for decision support and personal software.If the bulk of the application runs on the Server side, then it is Fat servers. It tries to minimize network interchanges by creating more abstract levels of services.

It includes the communication stacks, distributed directories, authentication services, network time, RPC, Queuing services along with the network OS extensions such as the distributed file and print services.

It is needed to accomplish a particular Client/Server type of services which includes:Database specific middlewareOLTP specific middlewareGroupware specific middlewareObject specific middlewareInternet specific middleware andSystem management specific 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.The middleware buliding block runs on both the client and server sides of an application. It is broken into three categoriesTransport stackNetwork OSService-specific middleware.

It waits for client-initiated requests.Executes many requests at the same time.Takes care of VIP clients first.Initiates and runs background task activity.Keeps running.Grown bigger and faster.

Base services - It is a part of the standard OSExtended services - These are add-on modular software components that are layered on top of base service

Task preemptionTask prioritySemaphoresInterprocess communications (IPC)Local/Remote Interprocess communicationThreadsIntertask protectionMultiuser High performance file systemEfficient memory management and Dynamically linked Run-time extensions

Ubiquitous communicationsNetwork OS extensionBinary large objects (BLOBs)Global directories and Network yellow pagesAuthentication and Authorization servicesSystem managementNetwork timeDatabase and transaction servicesInternet servicesObject- oriented services

These are fully-loaded machines which includes multiprocessors, high-speed disk arrays for intervive I/O and fault tolerant features. What are the two forms of Multi-processing

It treats all processors as equal. Any processor can do the work of any other processor. Applications are divided into threads that can run concurrently on any available processor. Any processor in the pool can run the OS kernel and execute user-written threads.

Non-GUI Client: These are applications, generate server requests with a minimal amount of human interaction.GUI Clients: These are applicatoins, where occassional requests to the server result from a human interacting with a GUI(Example: Windows 3.x, NT 3.5)OOUI clients : These are applications, which are highly-iconic, object-oriented user interface that provides seamless access to information in...

The types of transparencies the NOS middleware is expected to provide are Location transparencyNamespace transparencyLogon transparencyReplication transparencyLocal/Remote access transparencyDistributed time transparencyFailure transparency and Administration transparency.

RPC hides the intricacies of the network by using the ordinary procedure call mechanism familiar to every programmer. A client process calls a function on a remote server and suspends itself until it gets back the results. Parameters are passed like in any ordinary procedure. The RPC, like an ordinary procedure, is synchoronous. The process that issues the call waits until it gets the results. Under...

MOM allows general purpose messages to be exchanged in a Client/Server system using message queues. Applications communicate over networks by simply putting messages in the queues and getting messages from queues. It typically provides a very simple high level APIs to its services.MOM's messaging and queuing allow clients and servers to communicate across a network without being linked by a private,...

SQL is a powerful set-oriented  language which was developed by IBM research for the databases that adhere to the relational model. It consists of a short list of powerful, yet highly flexible, commands that can be used to manipulate information collected in tables. Through SQL, we can manipulate and control sets of records at a time.

SQL is an interactive query language for ad hoc database queries.SQL is a database programming language.SQL is a data definition and data administration language.SQL is the language of networked database serversSQL helps protect the data in a multi-user networked environment.Because of these multifacted roles it plays, physicists might call SQL as "The grand unified theory of database".

Process-per-client Architecture. (Example: Oracle 6, Informix )Multithreaded Architecture. (Example: Sybase, SQL server)Hybrid Architecture (Example: Oracle 7) 

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.