A comparison of flexible schemas for software as a service

Abstract

A multi-tenant database system for Software as a Service (SaaS) should offer schemas that are flexible in that they can be extended for different versions of the application and dynamically modified while the system is on-line. This paper presents an experimental comparison of five techniques for implementing flexible schemas for SaaS. In three of these techniques, the database "owns" the schema in that its structure is explicitly defined in DDL. Included here is the commonly-used mapping where each tenant is given their own private tables, which we take as the baseline, and a mapping that employs Sparse Columns in Microsoft SQL Server. These techniques perform well, however they offer only limited support for schema evolution in the presence of existing data. Moreover they do not scale beyond a certain level. In the other two techniques, the application "owns" the schema in that it is mapped into generic structures in the database. Included here are XML in DB2 and Pivot Tables in HBase. These techniques give the application complete control over schema evolution, however they can produce a significant decrease in performance. We conclude that the ideal database for SaaS has not yet been developed and offer some suggestions as to how it should be designed.

A Framework for the Evaluation of Saas Impact

“…The degree of isolation of a SaaS application may vary significantly depending on the business requirements and there are different techniques for implementing flexible schemas for SaaS. There are opinions that it should be possible to dynamically evolve the schema of the database, online and in "self-service" mode for each tenant, otherwise the SaaS provider has very high operational costs [2]. Authors like Aulbach, Jacobs, Kemper, & Seibold suggest techniques such as the use of XML columns and Pivot Tables [2].…”

Proxy Service for Multi-tenant Database Access

“…Nevertheless, these techniques are still not overcoming multi-tenant database challenges [1]. Salesforce.com, the pioneer of SaaS CRM applications has designed and developed a storage model to manage its virtual database structure by using a set of metadata, universal data table, and pivot tables which get converted to objects that the Universal Data Dictionary (UDD) keeps track of them, their fields and relationships, and other object definition characteristics.…”

“…Nevertheless, these techniques are still not overcoming multi-tenant database challenges [1]. NoSQL stands for Not Only Structured Query Language, is a non-relational database management system.…”

Data Combination Privacy Preservation Adjusting Mechanism for Software as a Service

“…And there are many research on the shared data schema [1][2] [3] for SaaS. Salesforce.com proposed the multi-tenancy platform Force.com, and presented the meta-data driven multi-tenancy architecture [4].…”