The OO7 Benchmark represents a comprehensive test of OODBMS performance. In this report we describe the benchmark and present performance results from its implementation in four OODB systems. It is our hope that the OO7 Benchmark will provide useful insight for end-users evaluating the performance of OODB systems; we also hope that the research community will nd that OO7 provides a database schema, instance, and workload that is useful for evaluating new techniques and algorithms for OODBMS implementation.

SHORE (Scalable Heterogeneous Object REpository) is a persistent object system under development at the University of Wisconsin. SHORE represents a merger of objectoriented database and file system technologies. In this paper we give the goals and motivation for SHORE, and describe how SHORE provides features of both technologies. We also describe some novel aspects of the SHORE architecture, including a symmetric peer-to-peer server architecture, server customization through an extensible value-added server facility, and support for scalability on multiprocessor systems. An initial version of SHORE is already operational, and we expect a release of Version 1 in mid-1994. 1 Introduction SHORE (Scalable Heterogeneous Object REpository) is a new persistent object system under development at the University of Wisconsin that represents a merger of object-oriented database (OODB) and file system technologies. While the past few years have seen significant progress in the OODB area, most ap...

This paper presents a portable, efficient method for accessing memory resident persistent objects in virtual memory in the context of the E programming language. Under the approach, objects are copied from the buffer pool of the underlying object manager into virtual memory on demand, as they are accessed by an E program. The cumulative effects of updates to a persistent object are then propagated back to the object manager via a single write operation at the end of each transaction. The method incorporates a comprehensive pointer swizzling mechanism to enhance performance. Swizzling is done a pointer-at-a-time and software checks are used to detect the use of swizzled pointers. The paper also presents the results of a performance study comparing the method presented here with several alternative software architectures including ObjectStore V1.2, a commercially available OODBMS. The results highlight the tradeoffs between providing software vs. memory-mapped support for pointer swizzli...

ing with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works, requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept, ACM Inc., 1515 Broadway, New York, NY 10036 USA, fax +1 (212) 869-0481, or permissions@acm.org. 2 \Delta M. J. Franklin et al. 1. INTRODUCTION 1.1 Client-Server Database System Architectures Advances in distributed computing and object-orientation have combined to bring about the development of a new class of database systems. These systems employ a client-server computing model to provide both responsiveness to users and support for complex, shared data in a distributed environment. Current relational DBMS products are based on a query-shipping approach in which most query processing is performed at servers; clients are primarily used to manage the user interface. In contrast, object-oriented database systems (OODBMS), whi...

This paper presents, QuickStore, a memory-mapped storage system for persistent C++ built on top of the EXODUS Storage Manager. QuickStore provides fast access to in-memory objects by allowing application programs to access objects via normal virtual memory pointers. The paper also presents the results of a detailed performance study using the OO7 benchmark. The study compares the performance of QuickStore with the latest implementation of the E programming language. These systems (QuickStore and E) exemplify the two basic approaches (hardware and software) that have been used to implement persistence in object-oriented database systems. In addition, both systems use the same underlying storage manager and compiler allowing us to make a truly applesto-apples comparison of the hardware and software techniques. 1.

Abstract. Collaborative knowledge base (KB) authoring environments are critical for the construction of high-performance KBs. Such environments must support rapid construction of KBs by a collaborative e ort of teams of knowledge engineers through reuse of existing knowledge and software components. They should support the manipulation of knowledge by diverse problem-solving engines even if that knowledge is encoded in di erent languages and by di erent researchers. They should support large KBs and provide a scalable and interoperable development infrastructure. In this paper, we present anenvironment that satis es many of these goals. We present an architecture for scalable frame representation systems (FRSs). The Generic Frame Protocol (GFP) provides infrastructure for reuse of software components. It is a procedural interface to frame representation systems that provides a common means of accessing and modifying frame KBs. The Generic KB Editor (Gkb-Editor) provides graphical KB browsing, editing, and comprehension services for large KBs. Scalability of loading and saving time is provided by a storage system (PERK) which submerges a database management system in an FRS. Multi-user access is controlled through a collaboration subsystem that uses a novel optimistic concurrency control algorithm. All the results have been implemented and tested in the development of several real KBs.

In this paper we develop and evaluate a number of storage reclamation algorithms for client-server persistent object stores. Experience with a detailed simulation and a prototype implementation in the Exodus storage manager shows that one of our proposed algorithms, the Incremental Partitioned Collector, is complete, maintains transaction semantics, and can be run incrementally and concurrently with client applications. Furthermore, it can significantly improve subsequent system performance by reclustering data, rendering it attractive even for systems that choose not to support automatic storage reclamation. 1 Introduction Experience with object-oriented programming languages has demonstrated that explicit storage management by programmers is a difficult and error prone task --- anyone who has spent time trying to find a storage leak in a non-trivial C++ program can attest to that fact. Fortunately, in C++ programs the effect of a storage leak is limited to individual runs of progra...

We describe an efficient server-based algorithm for garbage collecting object-oriented databases in a workstation/server environment. The algorithm is incremental and runs concurrently with client transactions, however, it does not hold any locks on data and does not require callbacks to clients. It is fault tolerant, but performs very little logging. The algorithm has been designed to be integrated into existing OODB systems, and therefore it works with standard implementation techniques such as two-phase locking and write-ahead-logging. In addition, it supports client-server performance optimizations such as client caching and flexible management of client buffers. We describe an implementation of the algorithm in the EXODUS storage manager and present results from an initial performance study of the implementation. These results demonstrate that the introduction of the garbage collector adds minimal overhead to client operations. 1 Introduction A primary strength of Object Oriented...

Current client-server object database management systems employ either a page server or an object server architecture. Both of these architectures have their respective strengths, but they also have key drawbacks for important system and workload configurations. We propose a new hybrid server architecture which combines the best features of both page server and object server architectures while avoiding their problems. The new architecture incorporates new or adapted versions of data transfer, recovery, and cache consistency algorithms; in this paper we focus only on the data transfer and recovery issues. The data transfer mechanism allows the hybrid server to dynamically behave as both page and object server. The performance comparison of the hybrid server with object and page servers indicates that the performance of the hybrid server is more robust than the others.

Distributed database systems need commit processing so that transactions executing on them still preserve the ACID property. With the advance of main memory database systems which become possible due to dropping price and increasing capacity of the RAM and CPU, the database processing speed has been incresed in one order of magnitude. However, when it comes to distributed commit processing, it is still very slow since disk logging has to precede the transaction commit where the database access does not incur any disk access at all in the case of main memory databases. In this paper, we re-evaluate the various distributed commit protocols' and come up with a single phase distributed commit protocol suitable for the distributed main memory database systems. Our simulation study confirms that the new protocol greatly reduces the time it takes to commit distributed transactions without any consistency problem.