The distributed measurement system JEWEL, developed within project RelaX, is described. JEWEL consists of a flexible toolkit for low-interference online performance measurement integrated with a powerful adaptable graphical presentation facility and a generic interactive experiment control system. JEWEL supports a large set of different system models as well as a wide variety of interfaces to the observed system. Two examples are presented in order to demonstrate its flexibility.>

The authors provide a description of RelaX (reliable distributed applications support on UniX), a portable and extensible system software layer on top of UNIX-like operating system kernels that supports reliable distributed applications by a generalized transaction mechanism. The transaction mechanism relieves each programmer of dealing explicitly with error recovery and concurrency control in every distributed application. In order to make transactions applicable as a general programming tool, flexibility has been introduced into the traditional transaction concept. The transaction mechanism is isolated in a server (Transaction Manager) that cooperates with an extensible set of resource managers, which provide different kinds of long-term storage entities accessible by RelaX transactions. Each resource manager provides a standard interface to the transaction kernel, and, if so desired, additional resource managers can be built. In order to ease the construction of new resource managers, RelaX provides generic software components as building blocks for any kind of resource manager. The RelaX architecture is described and the design of an examplary resource manager, the transactional object management system which provides access to persistent shared objects, is outlined.>