#multi_tenancy

Multi-tenancy is an architecture in which a single instance of a software application serves multiple customers. Each customer is called a tenant. Tenants may be given the ability to customize some parts of the application, such as color of the user interface (UI) or business rules, but they cannot customize the application's code.

Multi-tenancy can be economical because software development and maintenance costs are shared. It can be contrasted with single-tenancy, an architecture in which each customer has their own software instance and may be given access to code. With a multi-tenancy architecture, the provider only has to make updates once. With a single-tenancy architecture, the provider has to touch multiple instances of the software in order to make updates.

In cloud computing, the meaning of multi-tenancy architecture has broadened because of new service models that take advantage of virtualization and remote access. A software-as-a-service (SaaS) provider, for example, can run one instance of its application on one instance of a database and provide web access to multiple customers. In such a scenario, each tenant's data is isolated and remains invisible to other tenants.

http://whatis.techtarget.com/definition/multi-tenancy

Multitenancy is a reference to the mode of operation of software where multiple independent instances of one or multiple applications operate in a shared environment. The instances (tenants) are logically isolated, but physically integrated. The degree of logical isolation must be complete, but the degree of physical integration will vary. The more physical integration, the harder it is to preserve the logical isolation. The tenants (application instances) can be representations of organizations that obtained access to the multitenant application (this is the scenario of an ISV offering services of an application to multiple customer organizations). The tenants may also be multiple applications competing for shared underlying resources (this is the scenario of a private or public cloud where multiple applications are offered in a common cloud environment).

http://www.gartner.com/it-glossary/multitenancy

The term "software multitenancy" refers to a software architecture in which a single instance of software runs on a server and serves multiple tenants. A tenant is a group of users who share a common access with specific privileges to the software instance. With a multitenant architecture, a software application is designed to provide every tenant a dedicated share of the instance - including its data, configuration, user management, tenant individual functionality and non-functional properties. Multitenancy contrasts with multi-instance architectures, where separate software instances operate on behalf of different tenants.

Krebs, Rouven (2012). "Architectural Concerns in Multi-tenant SaaS Applications" (PDF). Proceedings of the 2nd International Conference on Cloud Computing and Services Science (CLOSER 2012). Conference on Cloud Computing and Services Science. SciTePress.

https://en.wikipedia.org/wiki/Multitenancy

Multi-tenancy is a situation in which many different users access the same system and the system architecture is defined to allow the efficient sharing of system resources. However, it must appear to each user that they have the sole use of the system. Multi-tenancy involves designing the system so that there is an absolute separation between the system functionality and the system data. You should, therefore, design the system so that all operations are stateless. Data should either be provided by the client or should be available in a storage system or database that can be accessed from any system instance. Relational databases are not ideal for providing multi-tenancy and large service providers, such as Google, have implemented a simpler database for user data. A particular problem in multi-tenant systems is data management. The simplest way to provide data management is for each customer to have their own database, which they may use and configure as they wish. However, this requires the service provider to maintain many different database instances (one per customer) and to make these available on demand. This is inefficient in terms of server capacity and increases the overall cost of the service. As an alternative, the service provider can use a single database with different users being virtually isolated within that database