Abstract. In this paper we present a new algorithm, DBMIN, for managing the buffer pool of a relational database management system. DBMIN is based on a new model of relational query behavior, the query locality set model (QLSM). Like the hot set model, the QLSM has an advantage over the stochastic models due to its ability to predict future reference behavior. However, the QLSM avoids the potential problems of the hot set model by separating the modeling of reference behavior from any particular buffer management algorithm. After introducing the QLSM and describing the DBMIN algorithm, we present a performance evaluation methodology for evaluating buffer management algorithms in a multiuser environment. This methodology employed a hybrid model that combines features of both trace-driven and distribution-driven simulation models. Using this model, the performance of the DBMIN algorithm in a multiuser environment is compared with that of the hot set algorithm and four more traditional buffer replacement algorithms.Key Words. Buffer management, Database systems, Page replacement strategies, Hybrid simulation, Performance evaluation.1. Introduction. In this paper we present a new algorithm, DBMIN, for managing the buffer pool of a relational database management system. DBMIN is based on a new model of relational query behavior, the query locality set model (QLSM.) Like the hot set model [Sacc 1], the QLSM has an advantage over stochastic models due to its ability to predict future reference behavior. However, the QLSM avoids the potential problems of the hot set model by separating the modeling of reference behavior from any particular buffer management algorithm. After introducing the QLSM and describing the DBMIN algorithm, the performance of the DBMIN algorithm in a multiuser environment is compared with that of the hot set algorithm and four more traditional buffer replacement algorithms.A number of factors motivated this research. First, although Stonebraker [Ston 2] convincingly argued that conventional virtual memory page replacement algorithms (e.g., least recently used (LRU)) were generally not suitable for a
Presented in this paper is the data model for ORION, a prototype database system that adds persistence and sharability to objects created and manipulated in object-oriented applications. The ORION data model consolidates and modifies a number of major concepts found in many objectoriented systems, such as objects, classes, class lattice, methods, and inheritance. These concepts are reviewed and three major enhancements to the conventional object-oriented data model, namely, schema evolution, composite objects, and versions, are elaborated upon. Schema evolution is the ability to dynamically make changes to the class definitions and the structure of the class lattice. Composite objects are recursive collections of exclusive components that are treated as units of storage, retrieval, and integrity enforcement. Versions are variations of the same object that are related by the history of their derivation. These enhancements are strongly motivated by the data management requirements of the ORION applications from the domains of artificial intelligence, computer-aided design and manufacturing, and office information systems with multimedia documents.
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We describe the implementation of a flexible data storage system for the UNIX environment that has been designed as an experimental vehicle for building database management systems. The storage component forms a foundation upon which a variety of database systems can be constructed including support for unconventional types of data. We describe the system architecture, the design decisions incorporated within its implementation, our experiences in developing this large piece of software, and the applications that have been built on top of it.
There are two major issues to address to achieve integration of an object-oriented programming system with a database system. One is the language issue: an object-oriented programming language must be augmented with semantic data modeling concepts to provide a robust set of data modeling concepts to allow modeling of entities for important real-world applications. Another is the computational-model issue: application programmers should be able to access and manipulate objects as though the objects are in an infinite virtual memory: in other words, they should not have to be aware of the existence of a database system in their computations with the data structures the programming language allows. This paper discusses these issues and presents the solutions which we have incorporated into the ORION object-oriented database system at MCC.
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