Information systems design has undergone significant change in terms of implementation strategies. Advances in networks have played a catalytic role in information systems with distributed databases.

Clifford defines a distributed database as a “computing system that contains a number of autonomous database management systems that are interconnected by a network and that cooperate with each other when performing data access and data capture tasks.” This book is mainly concerned with the Sybase replication server (RS), an asynchronous mechanism that supports the continuous replication and distribution of subscribed transactions. Such a facility is classified in the book as a loosely coupled, point-to-point, semi-autonomous, asynchronous data distribution system. The basic replication system is made up of SQL servers, log transfer managers (LTMs), and replication servers (RSs) under UNIX.

Chapter 2 describes an RS that contains multiple threads, domains, and internal libraries. All the components are described in detail.

The RS has its own Sybase database containing information about rejected transactions, recovery information, and error logs. The next chapter describes LTM, which is an open client/server application concerned with the transaction log, changes in the SQL server database, and message passing to RS. Chapter 5 describes the special RS called “ID Server,” whose main function is to register all RSs and SQL server databases. Messages are handled by the software module Stable Queue (SQ) under the control of RS, as shown in chapter 6.

Chapter 7 covers the important topic of bringing a new SQL server into the replication system. The working of the RS in terms of functions, calls, and strings is the subject of chapter 8. Chapter 9 describes extensions of Transaction-SQL to limit changes to an object of a database.

Security is an important aspect of distributed databases. Authorized users are discussed in chapter 10. Chapter 11 explores recovery of various components of the RS.

Chapter 12 is concerned with coordination of various components of the RS, and covers updates of RS parameters. The last chapter describes the replication server manager, which monitors all components of a specific replication system, and briefly describes commands.

Appendix A contains a case study of an RS implementation. Appendix B has a list of questions to help database administrators gain facility with details of the RS.

The index and glossary are adequate and useful, but there are no references. The author should have mentioned, at least, relevant Sybase manuals.

This book is an important addition to the literature on distributed databases. It is particularly useful to database administrators, EDP managers, and senior systems analysts. The presentation is excellent, though the book would have been more useful if more examples had been provided.