By exploiting a well known security vulnerability in many C library implementations, it is possible for an unprivileged user to gain unrestricted system privileges. With an understanding of how the process execution stack is allocated and managed during process execution, a user can override the return address of a C library routine and thereby resume execution at a different address where a set of malicious functions can be invoked [1]. This is known as the buffer overflow exploit. With buffer overflow as the underlying theme, an example will be described using C and the MIPS assembly language that simultaneously exposes students to issues in computer security, operating systems concepts such as memory management and function invocation/return, and the MIPS instruction set architecture.

A study is made of the issues in parallelizing database production systems. Various kinds of parallelism possible in production systems are classified. Parallel execution of production systems leads to some subtle problems which, if not handled carefully, can cause altered execution semantics. The precise conditions that any parallel implementation of production systems must fulfil in order to be semantically consistent are identified. A mechanism that guarantees the semantic consistency of parallel execution and proves its correctness is presented. It is based on a novel locking mechanism that provides more parallelism than conventional two-phase locking. The various factors that can affect the actual speedup of a database production system are discussed.>

The domain of statistical and scientific databases is targeted here, and the class of aggregate queries which are very often encountered in this domain is considered. Such a query is aimed at retrieving some aggregate characteristics of the raw data. The tree-based statistics access method (TBSAM), which provides support for the efficient processing of aggregate queries, is presented. It is related to the B/sup +/-tree and also processes the B/sup +/-tree's efficient update properties. Complementing TBSAM is the provision of a grouped update algorithm for minimizing expensive indexed database updates.>