For reasons of simplicity and communication efficiency, a number of existing object-oriented database management systems are based on page server architectures; data pages are their minimum unit of transfer and client caching. Despite their efficiency, page servers are often criticized as being too restrictive when it comes to concurrency, as existing systems use pages as the minimum locking unit as well. In this paper we showhow to support object-level locking in a page server context. Several approaches are described, including an adaptive granularity approach that uses page-level locking for most pages but switches to object-level locking when finer-grained sharing is demanded. We study the performance of these approaches, comparing them to both a pure page server and a pure object server. For the range of workloads that we have examined, our results indicate that a page server is clearly preferable to an object server. Moreover, the adaptive page server is shown to provide very good ...

A decade ago, the connection between objects and databases was new and was being explored in a number of di erent ways within our community. Driven by the perception that managing traditional business data was largely a solved problem, projects data types to relational databases and building extensible database systems, objectoriented database systems, and toolkits for constructing special-purpose database systems. In addition, work was underway elsewhere in the computer science research community on extending programming languages with database-inspired features such aspersistence and transactions. In this paper, we take a look at where our eld was a decade ago and where it is now in terms of database support for objects (and vice versa). We look both at research projects and at commercial database products. We share our vision and our biases about the future of objects and databases, and we identify anumber of research challenges that remain to be addressed in order to ultimately achieve our vision.

Association rule mining is a valuable decision support technique that can be used to analyze customer preferences, buying patterns, and product correlations. Current systems are however handicapped by the long processing times required by mining algorithms that make them unsuitable for interactive use. In this paper, we propose the use of a knowledge cache that can reduce the response time by several orders of magnitude. Most of the performance gain comes from the idea of guaranteed support that allows us to completely eliminate database accesses in a large number of cases. Using this cache, the time taken to answer a query is proportional to just the size of the result, rather than to the size of the database. Cache replacement is best done by a benefit-metric based strategy that can easily adapt to changing query patterns. We show that our caching scheme is quite robust, providing good performance on a wide variety of data distributions even for small cache sizes. We also compare alg...

Traditional database system architectures face a rapidly evolving operating environment, where millions of users store and access terabytes of data. In order to cope with increasing demands for performance, high-end DBMS employ parallel processing techniques coupled with a plethora of sophisticated features. However, the widely adopted, work-centric, thread-parallel execution model entails several shortcomings that limit server performance when executing workloads with changing requirements. Moreover, the monolithic approach in DBMS software has lead to complexanddifficulttoextenddesigns.

We present the design of an interface to allow applications to export tuning alternatives to a higher-level system. By exposing different parameters that can be changed at runtime, applications can be made to adapt to changes in their execution environment due to other programs, or the addition or deletion of nodes, communication links etc. An integral part of this interface is that an application not only expose its options, but also the resource utilization of each option and the effect that the option will have on the application's performance. We discuss how these options can be evaluated to tune the overall performance of a collection of applications in the system. Finally, we show preliminary results from a database application that is automatically reconfigured by the system from query shipping to data shipping based on the number of active clients.

The Collection Programming Language (CPL) is based on a complex value model of data, and has successfully been used for querying, transforming and integrating data from a wide variety of structured data sources -- relational, ACeDB, and ASN.1 among others. However, since there is no notion of objects and classes in CPL, it cannot adequately model recursive types or inheritance, and hence cannot be used to query object-oriented databases (OODBs). By adding a reference type and four operations to CPL -- dereference, method invocation, identity test and class type cast -- it is possible to express a large class of interesting "safe" queries against OODBs. As an example of how the extended CPL can be used to query an OODB, we will describe how the extended language has been used as a query interface to Shore databases. 1 Introduction A vast amount of data currently exists in databases, files formatted according to various data exchange formats, and application programs. Although much of t...

The spatial query has been processed in two steps, the filter step and the refinement step, due to a large volume and high complexity of the spatial data. However, this approach has been considered only in the query execution phase after completing the query optimization phase. This paper presents query optimization strategies which take the characteristics of spatial databases into account. The first strategy is the separation of filter and refinement steps not in the query execution phase but in the query optimization phase. As the second strategy, several refinement operations can be combined in processing a complex query, and as the third strategy several filter operations can also be combined. We call the optimization technique utilizing these strategies the Early Separated Filter And Refinement (ESFAR). This paper also presents a rule-based optimization technique for ESFAR. 1. Introduction For the past several years, the research on spatial database systems has actively progres...

An efficient index structure for complex multi-dimensional objects is one of the most challenging requirements in non-traditional applications such as geographic information systems, computer-aided design, and multimedia databases. This paper presents a multi-dimensional index structure based on a novel object decomposition method. This is an extension of an existing index structure. The proposed index structure integrates two index structures, one for original objects and the other for their decomposed components. An analytical model is developed for our index structure. The performance of our index structure is compared with that of a state-of-the-art index structure by experimental measurements. Our index structure outperforms the state-of-the-art index structure due to its ability to reduce a large amount of storage. Additionally, our index structure is easier to implement and applicable to various spatial data such as curves, regions, and volumes. This work was supported by the Na...

Shared Distributed Memory Systems offer uniform access to data which are distributed on servers. The Workspace model is a model of shared distributed memory. It is based on communicating processes which are both clients and servers. It enables to implement hierarchical views of data, to enhance security and it adapts to heterogenous networks. Keywords: Distributed Systems; Object-Oriented Database Systems; Storage Management. 1. Introduction. Database systems were first used on mainframes, and remain one of their major utilizations. As workstations display ever growing processing power and memory size, mainframes are less and less used, and their functions are often distributed between minicomputers and workstations. This favours the development of the Client-Server model, in which each client accesses one or more servers. The server may implement data shipping, or query shipping. Query shipping corresponds to the old access model where a mainframe was accessed by terminals. Wh...

This paper investigates the natural