As XML gains popularity as the standard data representation model, there is a need to store, retrieve and update XML data efficiently. McXml is a native XML database system that has been developed at McGill University and represents XML data as trees. McXML supports both read-only queries and six different kinds of update operations. To support concurrent access to documents in the McXML database, we propose a concurrency control protocol called LockX which applies locking to the nodes in the XML tree. LockX maximizes concurrency by considering the semantics of McXML's read and write operations in its design. We evaluate the performance of LockX as we vary factors such as the structure of the XML document and the proportion of read operations in transactions. We also evaluate LockX's performance on the XMark benchmark [16] after extending it with suitable update operations [13]. Finally, we compare LockX's performance with two snapshot-based concurrency control protocols (SnaX, OptiX) that provide a committed snapshot of the data for client operations.

We present storage organization schemes and a tuple density model of a relation, for the efficient processing of information in a relational database. The underlying concept used in the design of the storage schemes and the density model is that of a multidimensional array. These organizational schemes are: Multidimensional Paging, Dynamic Multipaging, and two dynamic multidimensional hashing schemes, DMHL and DMHE. The DMHL and DMHE schemes are the respective extensions of linear hashing and extendible hashing for multidimensional data organization. Storage mapping functions for extendible arrays are developed as the page addressing functions in the dynamic multidimensional structures. Performance of the multipaging schemes are examined through empirical studies. / We show how relations are structured with these organizational methods to provide symmetric access to the data on any combination of attributes. Further we derive size estimation formulae for the result of the various relational operations using the density model.

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Database and database technology are having a major impact on the growing use of computers. The rising popularity of database systems for the management of data has resulted in an increasing number of systems. As the number grows, the difficulty in choosing the system which will best meet the requirements of a particular application also increases. Knowing how to choose the correct one for a given application is important.The purpose of this thesis is to compare two very commonly used Database Management Systems (ORACLE and RDB) at Ball State University by describing and listing the advantages of each of them as well as their weaknesses, giving a comprehensive study of their performances, user friendliness, limits, and to aid users and managers in obtaining a deeper knowledge of these two systems. / Department of Computer Science

Databases and database technology are having a major impact on the growing use of computers. It is fair to say that databases are playing a critical role in almost all areas where computers are used, including business, engineering, medicine, law, education, and library science, to name a few.At Ball State University, databases are very widely used among faculty, staff, and students. The common commercial database management system (DBMS) used in the university is ORACLE. Due to the extensive use of the system and the availability and easy access to alternative systems such as RDB/VMS, a comparative research is in order.This thesis is a comprehensive comparison between the two systems. It covers the differences in design, SQL codings, and the use of host programming language such as FORTRAN. It concentrates on the differences in memory usage, execution time, as well as the CPU time needed to precompile, link, and run. / Department of Computer Science