Using PVM to Implement a Parallel Database System 1 )

MIDAS (MunIch Parallel DAtabase System) is a parallel relational database system. It is well suited to serve as a platform for the exploration of various strategies in order to parallelize a rela-tional database system. This short paper depicts how the abstract architecture of MIDAS looks like. A detailed description shows the implementation of a MIDAS prototype on a network of UNIX workstations. The core of the MIDAS protoype is implemented using PVM. But pure PVM does not fulfil all demands in order to implement a parallel database system. We demonstrate how our implementation combines the PVM programming model with standard UNIX mechanisms. We use UNIX shared memory to enhance the efficiency of our implementation and we use access privileges to UNIX files to secure the database against unauthorized access. MIDAS has a client/server architecture (see figure 1). The MIDAS server provides a high level interface (SQL) to retrieve and manipulate efficiently the contents of a relational database. The database itself is stored in the filesystem provided by the implementation platform. MIDAS clients are database applications. They are sequential programs issuing transactions to the MIDAS server. Each transaction on its part consists of retrieval/update queries. A MIDAS client can run on any computer having access to the MIDAS server. 1) This research is directed by Prof. R. Bayer Ph.D. and is part of the more extensive project " Tools and Methods for Using Parallel Computer Architectures " executed at the dept. of computer science of the Technische Universität München since 1990 (sponsored by DFG contract SFB 342).