Large-scale data warehousing, data mining and scientific applications require the analysis of terabytes of factual data accumulated over long periods of time. Tape libraries are suitable for storing such mass data. The online analytical processing (OLAP) of this data typically leads to long-running aggregation queries joining the tape-resident fact relations with disk-resident dimension relations. During the join execution, the disks storing the dimension relations are often not dedicated to the join. They are subject to reads and writes invoked by concurrently running applications. In many cases, the performance of these concurrent applications should not be degraded too much by the processing of the join. We present an accurate model for analysing the performance of three different tape-disk join strategies in multi-query systems. The major contributions are: (a) a cost model considering tape and disk bandwidth, tape and disk latencies, available buffer sizes, CPU costs and the selectivity of filters on tape data; (b) disk queueing effects due to concurrent reads and writes at the disk; and (c) two disk scheduling strategies. We show the superiority of a disk scheduling strategy that gives preference to the servicing of the concurrent disk load. We present a strategy for dynamically selecting the most beneficial join algorithm and its parameters at run time. We have implemented the join strategies in a prototype system based on detailed simulations of secondary and tertiary storage devices. Our evaluations confirm that the model is very accurate and a suitable basis for run-time strategy decisions.

Workflow management systems (WfMSs) support the efficient, largely automated execution of business processes. However, using a WfMS typically requires implementing the application's control flow exclusively by the WfMS. This approach is powerful if the control flow is specified and implemented from scratch, but it has severe drawbacks if a WfMS is to be integrated within environments with existing solutions for implementing control flow. Usually, the existing solutions are too complex to be substituted by the WfMS all at once. Hence, the WfMS must support an incremental integration, i.e. the reuse of existing implementations of control flow as well as their incremental substitution. Extending the WfMS's functionality according to future application needs, e.g. by worklist and history management, must also be possible. In particular, at the beginning of an incremental integration process, only a limited amount of a WfMS's functionality is actually exploited by the workflow application. Later on, as the integration proceeds, more advanced requirements arise and demand the customization of the WfMS to the evolving application needs. In this paper, we present the architecture and implementation of a light-weight WfMS, coined Mentor-lite, which aims to overcome the above-mentioned shortcomings of conventional WfMSs. Mentor-lite supports an easy integration of workflow functionality into an existing environment, and can be tailored to specific workflow application needs.

Most multimedia applications require storage and retrieval of large amounts of continuous and discrete data at very high rates. Disk drives should be servicing such mixed workloads achieving low response times for discrete requests, while guaranteeing the uninterrupted delivery of continuous data. Disk scheduling algorithms for mixed workloads, although they play a central role in this task, have been overlooked by related multimedia research efforts, which so far have mostly concentrated on the scheduling of continuous requests only. The focus of this paper is on efficient disk I/O scheduling algorithms for mixed workloads in a multimedia storage server. We propose novel algorithms, a taxonomy of relevant algorithms, and study their performance through experimentation. Our results show that our proposed algorithms offer drastic improvements in discrete request average response times, low response-time variability, while serving continuous requests without interruptions.

Article Free Access Share on Stochastic service guarantees for continuous data on multi-zone disks Authors: Guido Nerjes Swiss Federal Institute of Technology (ETH), Institute of Information Systems, CH-8092 Zurich, Switzerland Swiss Federal Institute of Technology (ETH), Institute of Information Systems, CH-8092 Zurich, SwitzerlandView Profile , Peter Muth University of the Saarland, Department of Computer Science, D-66041 Saarbrücken, Germany University of the Saarland, Department of Computer Science, D-66041 Saarbrücken, GermanyView Profile , Gerhard Weikum University of the Saarland, Department of Computer Science, D-66041 Saarbrücken, Germany University of the Saarland, Department of Computer Science, D-66041 Saarbrücken, GermanyView Profile Authors Info & Claims PODS '97: Proceedings of the sixteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systemsMay 1997 Pages 154–160https://doi.org/10.1145/263661.263679Published:01 May 1997Publication History 21citation276DownloadsMetricsTotal Citations21Total Downloads276Last 12 Months8Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

MENTOR (“Middleware for Enterprise-Wide Workflow Management”) is a joint project of the University of the Saarland, the Union Bank of Switzerland, and ETH Zurich [1, 2, 3]. The focus of the project is on enterprise-wide workflow management. Workflows in this category may span multiple organizational units each unit having its own workflow server, involve a variety of heterogeneous information systems, and require many thousands of clients to interact with the workflow management system (WFMS). The project aims to develop a scalable and highly available environment for the execution and monitoring of workflows, seamlessly integrated with a specification and verification environment.

A locking protocol for object-oriented database systems (OODBSs) is presented. The protocol can exploit the semantics of methods invoked on encapsulated objects. Compared to conventional page-oriented or record-oriented concurrency control protocols, the proposed protocol greatly improves the possible concurrency because commutative method executions on the same object are not considered as a conflict. An OODBS application example is presented. The principle of open-nested transactions is reviewed. It is shown that, using the locking protocol in an open-nested transaction, the locks of a subtransaction are released when the subtransaction completes, and only a semantic lock is held further by the parent of the subtransaction.>

VODAK is a prototype of an object-oriented, distributed database system developed during the past five years at the Integrated Publication and Information Systems Institute (IPSI). The aim of demonstrating VODAK Open Nested Transactions is to provide insights into internals of database systems that are usually hidden from application programmers and users. By utilizing semantics of methods, VODAK Open Nested Transactions increase the degree of parallelism between concurrent transactions compared to conventional transaction management schemes. Demonstrating the difference in parallelism provides users with a “feeling” for internal database mechanisms, application programmers with information about the impact of transaction management on performance, and system developers with ideas how to improve their systems with respect to transaction management.

The V3 Video Server is a demonstration showing a multimedia application developed on top of the VODAK database management system. VODAK is a prototype of an object-oriented and distributed database management system (DBMS) developed at GMD-IPSI. The V3 Video Server allows a user to interactively store, retrieve, manipulate, and present analog and short digital video clips. A video clip consists of a sequence of pictures and corresponding sound. Several attributes like author, title, and a set of keywords are annotated. The highlights of the demonstration are as follows. (1) It is shown that an object-oriented database management systems is very useful for the development of multimedia applications. (2) The video server gives valuable hints for the development of an object-oriented database management system in direction to a multimedia database management system.

A systematic discussion of atomic commitment for heterogeneous database systems is presented. An analysis is given of two alternative protocols for atomic commitment: commitment of local transaction after or before the global commit or abort decision is made. The impact of the protocols on recovery and concurrency control is shown. Atomicity, consistency, isolation, and durability properties are achieved for global transactions. It is demonstrated that commitment before fits best to multilevel transactions. In this case, the commitment protocol causes no additional overhead and a higher degree of concurrency can be achieved.>

Multi-level transactions have received considerable attention as a framework for high-performance concurrency control methods. An inherent property of multi-level transactions is the need for compensating actions, since state-based recovery methods do no longer work correctly for transaction undo. The resulting requirement of operation logging adds to the complexity of crash recovery. In addition, multi-level recovery algorithms have to take into account that high-level actions are not necessarily atomic, e.g., if multiple pages are updated in a single action.

A nine-valued circuit model for test generation is introduced which takes care of multiple and repeated effects of a fault in sequential circuits. Using this model test sequences can be determined which allow multiple and repeated effects of faults on the internal state of a sequential circuit. Thus valid test sequences are derived where other known procedures, like the D-algorithm, do not find any test although one exists.