5949420
Indexing Alternatives for Multiversion Locking
In this paper, we present several options for extending single-version indexing schemes for use with multiversion two-phase locking. The proposed options are orthogonal to the underlying indexing structure (e.g., hashing or B+ trees). The options differ in where they place references to individual versions; this version selection information is placed either with the data or in the leaf entries of one or more indices. We also briefly summarize the results of a performance study showing that storing version selection information with the data is usually the best option because it keeps indices smaller, thus enabling a larger fraction of the indices to remain cached in the buffer pool.
1009208
Fine-grained sharing in a page server OODBMS
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 show how 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 performance, generally outperforming the pure page server, the pure object server, and the other alternatives as well.
5780278
A Status Report on the oo7 OODBMS Benchmarking Effort
The OO7 Benchmark was first published in 1993, and has since found a home in the marketing literature of various object-oriented database management system (OODBMS) vendors. The OO7 Benchmark (as published) was the initial result of an ongoing OODBMS performance evaluation effort at the University of Wisconsin. This paper provides an update on the status of the effort on two fronts: single-user and multi-user. On the single-user front, we review and critique the design of the initial OO7 Benchmark. We discuss some of its faults, the reasons for those faults, and things that might be done to correct them. On the multi-user front, we describe our current work on the development of a multi-user benchmark for OODBMSs. This effort includes changes and extensions to the OO7 database and the design of a family of interesting multi-user workloads.
16894136
Query processing in main memory database management systems
Most previous work in the area of main memory database systems has focused on the problem of developing query processing techniques that work well with a very large buffer pool. In this paper, we address query processing issues for memory resident relational databases, an environment with a very different set of costs and priorities. We present an architecture for a main memory DBMS, discussing the ways in which a memory resident database differs from a disk-based database. We then address the problem of processing relational queries in this architecture, considering alternative algorithms for selection, projection, and join operations and studying their performance. We show that a new index structure, the T Tree, works well for selection and join processing in memory resident databases. We also show that hashing methods work well for processing projections and joins, and that an old join method, sort-merge, still has a place in main memory.
28682270
Extending and solving a multiperiod congested network flow model
Abstract We consider an existing model for optimizing time-varying flows on a congested network, and extend it so as to improve its accuracy while reducing computation. The model has been developed in a series of articles and has a variety of applications. Solving the model is a significant problem, since it is a non-linear program and can be very large for even small or medium size applications. Hitherto the model has been solved by taking a piecewise linear approximation and solving this as a linear program, perhaps taking advantage of the staircase structure of the constraints. However, this staircase is not available in the extended model. Further, the existing solution methods do not take advantage of the network structure of the problem. Here we show that a piecewise linear version of the model can be stated as a pure processing network (PPN); this allows algorithms for PPNs to be used to solve the model. We also propose a penalty (or barrier) function solution method. This reduces the problem to successively reoptimizing a program equivalent to the well-known static traffic assignment model. The latter is a convex cost, linearly constrained, un capacitated network flow problem. The above solution methods apply both to the basic model and the extended model.