A Multi-tenant architecture is a cost optimization for Software as a Service, where customers, also referred to as tenants are consolidated into the same server. The main idea of this architecture is to consolidate as many tenants as possible into the same server to reduce the total cost for the service provider. However, the contention of shared resources can lead to reduced performance for the tenants. One shared resource between the tenants is the data-layer.This thesis aims to analyze and to do a performance evaluation of different data-layer designs in a Multi-tenant architecture. The thesis compares three data-layer designs implemented in a RDBMS.An experiment was performed to evaluate the transactions per secondfor tenants when both the amount of data and the number of tenants increase. The evaluations were computed for the Create, Read, Update and Delete operations, also known as the CRUD-operations.Three data-layer designs were tested in the experiment; Shared table design, where tenants share the same database system as well as the tables, Separated table design, where tenants share the same database system but store and query data to their own private tables and Oracle Multi-tenant, where each tenant gets its own database.The experiment indicates that the Oracle Multi-tenant has the highest performance while the Shared table design suffers when both the number of tenants and the amount of data increase. / Multi-tenant arkitektur är en kostnadsoptimering för mjukvara som tillhandahålls över ett nätverk. Användarna, tenants är då betjänade av samma serverdator. Uppdraget för serverdatorn är att betjäna så många tenants som möjligt för att reducera kostnader för mjukvaruägaren. Men att dela resurser mellan tenants kan leda till försämrad prestanda. En delad resurs mellan tenants är dataskiktet.Målet med denna uppsats är att göra en analys och ett prestandatest av olika uppsättningar av dataskikt i en Multi-tenant arkitektur. Uppsatsen fokuserar endast på olika uppsättningar i ett RDBMS.Ett experiment utfördes där antalet tenants och data ökade för varje uppsättning. Experimentet evaluerade prestanda av Create, Read, Update och Delete operationer, även känt som CRUD-operationer. Tre uppsättningar testades; Shared table design, där tenants delar databas och tabeller, Separated table design, där tenants delar databas, men lagrar data i sina egna tabeller och Oracle Multi-tenant, där varje tenant får en egen databas.Experiment visar att Oracle Multi-tenant har högst prestanda medan Shared table design har lägst när antalet tenants och mängd data ökar.

A Multi-tenant database (MTD) is a way of deploying a Database as a Service (DaaS). A multi-tenant database refers to a principle where a single instance of a Database Management System (DBMS) runs on a server, serving multiple clients organisations (tenants). This technology has helped to discard the large-scale investments in hardware and software resources, in upgrading them regularly and in expensive licences of application software used on in-house hosted database systems. This is gaining momentum with significant increase in the number of organisations ready to take advantage of the technology. The benefits of MTD are potentially enormous but for any organisation to venture into its adoption, there are some salient factors which must be well understood and examined before venturing into the concept. This research examines these factors, different models of MTD, consider the requirements and challenges of implementing MTDs. Investigation of the degree of impact each of these factors has on the adoption of MTD is conducted in this research which focused mainly on public organisations. The methodology adopted in undertaking this study is a mixed method which involved both qualitative and quantitative research approaches. These strategies are used here to cover statistics (quantifiable data) and experts’ knowledge and experiences (abstract data) in order to satisfactorily achieve the aim and objectives and complete the research. Following the involvement of these strategies, a framework was developed and further refined after a second survey was carried out with a quantitative approach. This framework will help prospective tenants to make informed decisions about the adoption of the concept. The research also considers the direction of decisions about MTDs in situations where two or more factors are combined. A new MTD framework is presented that improves the decision making process of MTD adoption. Also, an Expert System (ES) is developed from the framework which was validated via a survey and analysed with the aid of SPSS software. The findings from the validation indicated that the framework is valuable and suitable for use in practice since majority of respondents accepted the research findings and recommendations for success. Likewise, the ES was validated with majority of participants accepting it and embracing the high level of its friendliness.