What are different characteristics of Scalability Testing?

Scalability can be essentially defined as the ability of a software application, network, process or program to effective and gracefully handle the increasing workload and effectively and easily carry out the specified tasks assigned properly. Throughput is the best example for this ability of a software application.

- Scalability as such is very difficult to define without practical examples.
- Therefore, scalability is defined based on some dimensions.
- Scalability is very much needed in communication areas like in a network, in software applications, in handling huge databases and it is also a very important aspect in routers and networking.
- Software applications and systems having the property of scalability are called scalable software systems or applications.
- They improve throughput to surprising extent after addition of new hardware devices. Such systems are commonly known as scalable systems.
- Similarly if a design, network, systems protocol, program or algorithm is suitable and efficient enough and works well when applied to greater conditions and problems in which the input data is in large amount or the problem or situation has got several nodes, they are said to be efficiently scalable.

If, during the process of increasing the quantity of input data the program fails, the program is not said to scale. Scalability is so much needed in the field of information technology. Scalability can be measured in several dimensions. Scalability testing deals with testing of these dimensions only.

The kinds of scalability testing have been discussed in detail below:

- Functional scalability testing:
In this testing new functionalities which are added to the software application or the program to enhance and improve its overall working are tested.

- Geographic scalability testing:
This testing tests the ability of the software system or the application to maintain its performance and throughput, and usefulness irrespective of distributing of working nodes in some geographical pattern.

- Administrative scalability testing:
This testing deals with the increment of working nodes in software, so that a single difficult task is divided among smaller units making it much easier to accomplish.

- Load scalability testing:
This testing can be defined as the testing of the ability of a divided program to divide further and unite again to take light and heavy workload accordingly.

There are several examples available for scalability today. Few have been listed below:

- Routing table of the routing protocol which increases in extent with respect to the increase in the extent of network.
- DBMS (data base management system) is scalable in the sense that more and more data can be uploaded to it by adding new required devices.
- Online transaction processing system can also be stated as scalable as one can upgrade it and more transactions can be done easily at one time.
- Domain name system is a distributed system and works effectively even when the hosting is on the level of World Wide Web. It is scalable.

Scaling is done basically in two ways. These two ways have been discussed below:

- Scaling out or scaling horizontally: This method of involves addition of several nodes or work stations to an already divided or distributed software application. This method has led to the development of technologies namely batch processing management and remote maintenance which were not available before the discovery of this technology.

Scaling up or scaling vertically:
Scaling up or scaling vertically can be defined as the addition of hardware or software resources to any single node of the system. These resources can either be CPUs or memory devices. This method of scaling has led to a tremendous improvement in virtualization technology.