The Issues And Solutions Of Integrating DBMS To A Multi-DBMS

Many organizations invest heavily in heterogeneous databases according to organizational functions. These heterogeneous databases are stand-alone systems that do not interact with one another. The objective of this paper is to introduce a multi-database system (MDBMS) that interacts with other heterogeneous DBMS within the organization to integrate information processing. In this paper, we discuss the potential inconsistencies in integrating heterogeneous databases. We further extend to include issues in designing a MDBMS. With a MDBMS, data sharing across organization reduces overheads and costs, thus, provides a competitive advantage to the global firms

Towards interoperability in heterogeneous database systems

Distributed heterogeneous databases consist of systems which differ physically and logically, containing different data models and data manipulation languages. Although these databases are independently created and administered they must cooperate and interoperate. Users need to access and manipulate data from several databases and applications may require data from a wide variety of independent databases. Therefore, a new system architecture is required to manipulate and manage distinct and multiple databases, in a transparent way, while preserving their autonomy. This report contains an extensive survey on heterogeneous databases, analysing and comparing the different aspects, concepts and approaches related to the topic. It introduces an architecture to support interoperability among heterogeneous database systems. The architecture avoids the use of a centralised structure to assist in the different phases of the interoperability process. It aims to support scalability, and to assure privacy and nfidentiality of the data. The proposed architecture allows the databases to decide when to participate in the system, what type of data to share and with which other databases, thereby preserving their autonomy. The report also describes an approach to information discovery in the proposed architecture, without using any centralised structure as repositories and dictionaries, and broadcasting to all databases. It attempts to reduce the number of databases searched and to preserve the privacy of the shared data. The main idea is to visit a database that either containsthe requested data or knows about another database that possible contains this data

A comparative study of transaction management services in multidatabase heterogeneous systems

Multidatabases are being actively researched as a relatively new area in which many aspects are not yet fully understood. This area of transaction management in multidatabase systems still has many unresolved problems. The problem areas which this dissertation addresses are classification of multidatabase systems, global concurrency control, correctness criterion in a multidatabase environment, global deadlock detection, atomic commitment and crash recovery. A core group of research addressing these problems was identified and studied. The dissertation contributes to the multidatabase transaction management topic by introducing an alternative classification method for such multiple database systems; assessing existing research into transaction management schemes and based on this assessment, proposes a transaction processing model founded on the optimal properties of transaction management identified during the course of this research.ComputingM. Sc. (Computer Science

Global Semantic Integrity Constraint Checking for a System of Databases

In today’s emerging information systems, it is natural to have data distributed across multiple sites. We define a System of Databases (SyDb) as a collection of autonomous and heterogeneous databases. R-SyDb (System of Relational Databases) is a restricted form of SyDb, referring to a collection of relational databases, which are independent. Similarly, X-SyDb (System of XML Databases) refers to a collection of XML databases. Global integrity constraints ensure integrity and consistency of data spanning multiple databases. In this dissertation, we present (i) Constraint Checker, a general framework of a mobile agent based approach for checking global constraints on R-SyDb, and (ii) XConstraint Checker, a general framework for checking global XML constraints on X-SyDb. Furthermore, we formalize multiple efficient algorithms for varying semantic integrity constraints involving both arithmetic and aggregate predicates. The algorithms take as input an update statement, list of all global semantic integrity constraints with arithmetic predicates or aggregate predicates and outputs sub-constraints to be executed on remote sites. The algorithms are efficient since (i) constraint check is carried out at compile time, i.e. before executing update statement; hence we save time and resources by avoiding rollbacks, and (ii) the implementation exploits parallelism. We have also implemented a prototype of systems and algorithms for both R-SyDb and X-SyDb. We also present performance evaluations of the system

Concurrency Control in Multidatabases

Computer Science

Transactional actors in cooperative information systems

Transaction management in advanced distributed information systems is a very important issue under research scrutiny with many technical and open problems. Most of the research and development activities use conventional database technology to address this important issue. The transaction model presented in this thesis combines attractive properties of the actor model of computation with advanced database transaction concepts in an object-oriented environment to address transactional necessities of cooperative information systems. The novel notion of transaction tree in our model includes subtransactions as well as a rich collection of decision making, chronological ordering, and communication and synchronization constructs for them. Advanced concepts such as blocking/ non_blocking synchronization, vital and non_vital subtransactions , contingency transactions, temporal and value dependencies, and delegation are supported. Compensatable subtransactions are distinguished and early commit is accomplished in order to release resources and facilitate cooperative as well as longduration transactions. Automatic cancel procedures are provided to logically undo the effects of such commits if the global transaction fails. The complexity and semantics-orientation of advanced database applications is our main motivation to design and implement a high-level scripting language for the proposed transaction model. Database programming can gain in performance and problem-orientation if the semantic dependencies between transactions can be expressed directly. Simple and flexible mechanisms are provided for advanced users to query the databases, program their transactions accordingly, and accept weak forms of semantic coherence that allows for more concurrency. The transaction model is grafted onto the concurrent obj ect-oriented programming language Sather developed at UC Berkeley which has a nice high-level syntax, supports advanced obj ect-oriented concepts, and aims toward performance and reusability. W have augmented the language with distributed programming facilities and various types of message passing routines as well as advanced transactions management constructs . The thesis is organized in three parts. The first part introduces the problem, reviews state of the art, and presents the transaction model. The second part describes the scripting language and talks about implementation details. The third part presents the formal semantics of the transaction model using mathematical notations and concludes the thesis