Distributed Database Management System Research Articles

Integrating logic and object paradigm in HDDBMS

The existing heterogeneous distributed database management systems (HDDBMSs) which are business-oriented will not be able to adequate for many new and developing information processing applications. The important objectives of these applications include the processing of complex objects and intelligence. Our approach is integrating logic and object paradigm to provide knowledge representation and inference mechanism in HDDBMS. This paper decribes the knowledge representation in object-oriented heterogeneous distributed database system with semantic association — OHDDB-DG1, presents the method of processing constraints and rules in the global language OSAL which is Object-oriented and of Semantic Association with Logic, and explains briefly the peculiarities of processing inheritance and recursive inference.

Architecture of distributed data base systems

Research and development over the last twenty years has culminated in the widespread use of data base management system (DBMS) software. As usage has grown, the desire to link and integrate separate data bases has resulted in substantial effort being directed towards the design of distributed data base systems. This paper presents the major architectures which have emerged for distributed data base systems. The architectures are compared and evaluated. Sixteen distributed data base management system (DDBMS) projects have been surveyed and classified according to the architectures. The various projects represent widely differing stages of effort: academic research, industrial testbeds, and commercial prototypes. The survey reviews important features of the DDBMSs. It does not attempt a qualitative performance comparison. The focus is instead on identification of overall architectural characteristics. The usefulness of the survey lies in the summary information which it imparts on current research, and in the classification scheme for generic distributed data base architectures which it provides.

Detection of mutual inconsistency in distributed databases

A Distributed Database Management System should guarantee the consistency of databases at all sites in the system. In particular when the databases are replicated, mutual consistency among all copies of an item should be maintained. Network partitioning is a difficult kind of failure to deal with. A strategy known as the optimistic approach allows transactions to be run independently in different parts of the distributed system formed due to a partition. The mutual consistency among the copies of an item cannot be taken for granted in this scenario. Thus a natural requirement of the system then is that it determines whether or not the database is consistent and tries to resolve any inconsistencies. A simple scheme is presented in this paper to detect mutual inconsistency when partitioned databases merge. This scheme is similar to that of D. S. Parker et al. [ IEEE Trans. Software Eng. (May 1983)] in spirit although it is more general. In contrast to that of S. Davidson [ ACM Trans. Database Systems (Sept. 1984), 456–482] where a certain amount of information is maintained about each transaction run after the partition, our scheme maintains certain information with each data item accessed after the partition.

Communications costs under alternative distributed database configurations

Distributed database management systems (DDBMSs) can be configured in a variety of ways. Full or partial replication of data may be utilized, and even within systems not allowing replication a variety of directory configurations might be used, including fully replicated, centrally replicated and distributed directory systems. Alternative DDBMS configurations may lead to very different communications costs in a distributed network, and changes in database usage patterns are likely to affect different configurations in different ways. This paper models the communications costs associated with several alternative DDBMS configurations and examines the impact of changing database usage patterns on those costs. Changes in usage are found to have a substantial impact on relative communications costs of the alternative configurations.

Concurrency control in distributed databases through time intervals and short-term locks

A method for concurrency control in distributed database management systems that increases the level of concurrent execution of transactions, called ordering by serialization numbers (OSN), is proposed. The OSN method works in the certifier model and uses time-interval techniques in conjunction with short-term locks to provide serializability and prevent deadlocks. The scheduler is distributed, and the standard transaction execution policy is assumed, that is, the read and write operations are issued continuously during transaction execution. However, the write operations are copied into the database only when the transaction commits. The amount of concurrency provided by the OSN method is demonstrated by log classification. It is shown that the OSN method provides more concurrency than basic timestamp ordering and two-phase locking methods and handles successfully some logs which cannot be handled by any of the past methods. The complexity analysis of the algorithm indicates that the method works in a reasonable amount of time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Four reference architectures for distributed database management systems

Five requirements for a centralized database management system and five additional requirements for a distributed database management system suggest definitions of software processors and schemas. These software processors and schemas can be organized into four reference architectures for distributed database management systems which permit comparisons of their advantages and disadvantages.

Intent: an integrated environment for distributed heterogeneous databases

Intent: an integrated environment for distributed heterogeneous databases

Multilevel security issues in distributed database management systems

This paper describes the security needs in a distributed processing environment common to many enterprises and discusses the applicability of multilevel secure database management systems in such an environment.

The effects of two-phase locking on the performance of a distributed database management system

In this paper, the effects of two-phase locking on the performance of a distributed database management system are evaluated. In particular, the relationship between the average transaction response time for four concurrency control algorithms based on two-phase locking has been established with respect to the static degree of interference for a given multiprogramming level, database size, and transaction size. The increase in average probability of one lock request conflicting with another has been measured with respect to the static degree of interference and the percentage of aborted transactions has been measured for each algorithm. In addition, the impact of a number of parameters (e.g. data replication, lock predeclaration, time-out, local processing time, degree of locality of references, interarrival time, number of nodes and transmission time) on the performance of a distributed database management system in the presence of a concurrency control mechanism has also been measured. The study has been made using simulation and the SIMULA programming language.

The design and implementation of an OA system ZGL1

ZGL1, an office automation system for municipal administration, is presented. It is a distributed microcomputer system based on OMNINET. Each node of it is an IBM PC/XT microcomputer with Chinese character facilities. The system consists of a distributed database management system, a Chinese character electronic mail system, a Chinese word processor and others. Its functions include document management, report form management, research project management, finance management and information access.

An Evaluation of Precompilation and Interpretation in Distributed Database Management Systems

In this paper we present a simple model for the performance evaluation of Distributed Database Management Systems (DDBMS). We first define a transaction-processing model. Then we provide a set of expressions to evaluate the impact of various factors on the performance. The performance is evaluated in terms of transaction response time. Finally we compare the pre-compilation and the interpretation approaches using these expressions. briefly some of the studies that have focused on distributed database systems. Ries 17 compared four concurrency control algorithms, two based on centralised control and two based on distributed control. The centralised methods were variations of centralised two-phase locking; the differ- ence in the two algorithms was essentially concerning transaction scheduling. The distributed control methods differed in the way they solved the deadlock. In one, a deadlock detection algorithm was invoked periodically, in the other the 'wound-wait' model was adopted, which prevents deadlock situations. The simulation model used involved about twenty input parameters that described the database, the transactions, the sites and the network. Performance measures included I/O utilisation and average response time. The simulation results indicated that choice of the best algorithm in terms of the overall database system performance is application-dependent. However, the results indicated that when most trans- actions can be handled locally the distributed control leads to better performance, while if most transactions are non-local centralised control performs better. Lin and Nolte 14 have first evaluated the two-phase locking in a centralised DBMS. In the simulation model, the application environment is characterised by the trans- action size, and the system environment is characterised by the number of transactions running concurrently and the total number of lockable units. Performance

EDDS — a system to harmonize access to heterogeneous databases on distributed micros and mainframes

This paper presents the schema and component architectures of a prototype multidatabase management system, EDDS, which is used for research and teaching purposes in the authors' laboratories. Many of the features are shared with other distributed database management systems but some novel features, such as the gateway feature which allows personal computers to share distributed database functionality, are particularly attractive in many of the specific real-world scenarios for which the system was designed. The system is written in C on Unix, and in PASCAL on DEC VMS, and several PC ports have been implemented.

A retrospective of R*: A distributed database management system

This paper discusses the experience gained during the implementation of a prototype distributed database management system. The R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> prototype supports transparent distribution of a relational database which is accessed using the SQL language for data definition and manipulation. While supporting autonomy among the participating sites, R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> also emphasizes good performance for both local and multi-site operations. During the implementation of the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> prototype, we were guided by a few key objectives and encountered several interesting problems. This paper will discuss the guiding objectives of the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> effort, as well as several areas of the implementation which presented special difficulties or were simplified by design decisions.

An Ada-compatible distributed database management system

Adaplex is an integrated language for programming database applications. It results from the embedding of the database sublanguage Daplex in the general-purpose programming language Ada [1]. This paper describes the design of DDM, a general-purpose distributed database management system implemented in Ada that supports the use of Adaplex as interface language. There are two novel aspects in the design of this system. First, this is the first full-scale distributed database system to support a semantically rich, functional data model. DDM goes beyond systems like Distributed INGRES and R*(which are based on the relational technology) in providing advanced data modeling capabilities and ease of use. Second, this is the first full-function distributed DBMS designed to be compatible with the Ada programming environment. The coupling between Ada and Daplex has been achieved at the expression level which is much tighter than the statement level integration attained in previous systems. This tight coupling poses new implementation problems but also creates new opportunities for optimization. The current paper highlights the Adaplex language and discusses innovative aspects in DDM's design that are intended to meet the dual objectives of good performance and high data availability.

Some experiences with a distributed database testbed system

DDTS (Distributed Database Testbed System) was developed for the purpose of evaluating alternative approaches and algorithms for managing data stored in several databases on different machines. An overview of the system and information architectures of DDTS, as well as an example of the execution of a distributed request, are presented. The results of experiments with three query optimization algorithms are summerized. Our approach for dealing with semantic integrity constraints in a distributed system is reviewed. By sacrificing the enforcement of semantic integrity constraints that span sites, DDTS can be used as a federated distributed database management system.

Transaction management in the R* distributed database management system

This paper deals with the transaction management aspects of the R* distributed database system. It concentrates primarily on the description of the R * commit protocols, Presumed Abort (PA) and Presumed Commit (PC). PA and PC are extensions of the well-known, two-phase (2P) commit protocol. PA is optimized for read-only transactions and a class of multisite update transactions, and PC is optimized for other classes of multisite update transactions. The optimizations result in reduced intersite message traffic and log writes, and, consequently, a better response time. The paper also discusses R * 's approach toward distributed deadlock detection and resolution.

C-POREL——A DISTRIBUTED RELATIONAL DATA BASE MANAGEMENT SYSTEM ON MICROCOMPUTER NETWORK

In this paper we present a distributed relational data base management system on microcomputer network titled C-POREL. The design and implementation ideas of this system are based on the pioneer distributed data base management systems such as SDD-1, SIRIUSDELTA, ADA-DDM, R~* and especially POREL. The primary goal of C-POREL is practicability, with emphasis as well on the advancement, adaptability and limited portability. The microcomputers MC68000 connected by local network ETHERNET are selected to setup CPOREL. C-POREL is now implemented in the Institute of Mathematics, Academia Sinica,the Department of Computer Science, Shanghai University of Science and Technology and the Department of Computer Science, Normal University of East China.

Toward the Next Generation of Data Modeling Tools

This paper describes the Update Protocol Model (UPM), a formal language for the expression of database update semantics. UPM has been used primarily to capture and communicate in a precise and uniform notation the plethora of database semantics described by a variety of fourth generation models, many of which are imprecise when it comes to update semantics. Several computing trends–knowledge-based expert systems, distributed database management systems, and new applications based on higher order semantic models–point to the need for modeling techniques beyond that which current data models such as the relational and entity-relationship models provide.

Distributed Databases for Surveying

Space related data is gathered in different places and by different services. Considerable duplication of effort to maintain the same data is obvious. The use of a distributed database management system to manage such data collections is proposed. Information and data collection have special characteristics, which must be taken into account. They are expensive to update, but can easily be duplicated or transported from one place to another. Different users may produce or use the data and data may be an important asset for a user group. A distributed database may be adapted to such situations and most adequately suit managerial considerations. Users may maintain control over data of importance to them but nevertheless let other users gain access to it.

Microcomputers and distributed database management systems

The role of a DDBMS is to provide overall system integrity, appropriate data access, and recovery over the whole network. Many of the supermicros with powerful 16 and 32 bit architectures will soon be running advanced DBMS and DDBMS software, thus, playing an important role as a distributed database on a network. The article discusses this and future trends.