Hash-based scalable distributed data structures (SDDSs), like LH * and DDH, for networks of intcmonnected ampllters (multicomputers) were shown to open new perspectives for fik management. We prcpose a family of ordered SDDSs, called P, providing for ordered and dynamic files on mutticomputers, and thus for more etlicknt pmeessing of range queries and of ordered traversak of files The basic algorithm termed RP*K builds the file with the same key space partitioning as a Etree, but avoids indexes through the use of multi&. The a&nithms, RP*c and RP*s enbance throughput for faster network adding the indexes on clients, or OII clients and sexve-rs, while eithe-r decmsing or avoiding multicast. Rpo files are shown highly efficient with access performance exceeding traditional files by an order of magnitude or two, an & for non-range queries very close to LH*. 1.

The mobile wireless computing environment of the future will contain large numbers of low powered palmtop machines. Replication will be an essential technique in this environment, providing data availability to the system. In a mobile environment it is important to have dynamic replicated data management algorithms that allow for instance copies to migrate from one site to another or for new copies to be generated. In this paper we show that such dynamic algorithms can be obtained simply by letting transaction update the directory that specifies sites holding copies. Thus we argue that no fundamentally new algorithms are needed to cope with mobility. However, exisiting algorithms may have to be "tuned" for a mobile environment, and we discuss what this may entail. As an illustration, we present a variation of the primary copy algorithm, Primary By Row, that is well suited for migrating copies 1 . Keywords: Distributed Data Bases, replication, mobility, availability. 1 Intr...

Modern applications increasingly require scalable, highly available and distributed storage systems. High-availability schemes typically deliver data despite up to n 1 simultaneous unavailabilities of the storage nodes (disks, processors with storage, or entire computers), where n is fixed. Such schemes are insufficient for scalable files, since the probability of more than n failures increases arbitrarily with file size. We propose a new schema termed LH*sa withstanding up to n simultaneous unavailabilities with n scaling with the file. We present LH*sa file manipulation and recovery algorithms. We discuss the access and storage performance, and variants tuning selected features. We show that LH*sa files may scale to any number of nodes, keeping the probability of data unavailability arbitrarily small. 1

The considerable growth of on-line document searching and consulting brings much of the data providers to reconsider their database management systems (DBMS) capacities. Parallel DBMS then appear as a good solution, but the involved changes in administration and cost limit their breakthrough. To overcome these drawbacks, we propose an hybrid structure, which adapts a parallel extension to an existing DBMS. This extension cuts down the amount of work of the sequential DBMS, by parallelizing the incoming queries over a network of workstations. To allow this parallel execution, data are replicated over the stations according to a specific strategy. We describe this strategy and then examine the parallel query optimization. Keywords : Parallelism, Networks of Workstations, Relational Databases. 1. Introduction The last ten years have witnessed the arising of parallel techniques into Database Management Systems (DBMS), in order to provide quick access to large and very large databases to ...

. The considerable growth of on-line document searching and consulting brings much of the data providers to reconsider their database management systems (DBMS) capacities. Parallel DBMS then appear as a good solution, but the involved changes in administration and cost limit their breakthrough. To overcome these drawbacks, we propose an hybrid structure, which adapts a parallel extension to an existing DBMS. This extension cuts down the amount of work of the sequential DBMS, by parallelizing the incoming queries over a network of workstations communicating with PVM. Keywords : Parallelism, Networks of Workstations, Relational Databases. 1 Introduction The last ten years have witnessed the arising of parallel techniques into Database Management Systems (DBMS), in order to provide quick access to large and very large databases to many simultaneous users. Two domains are especially concerned : Online Transaction Processing (OLTP, i.e. business databases) and Query Processing (QP, i.e. da...

this paper we show that such dynamic algorithms can be obtained simply by letting transaction update the directory

LH* schema is among most studied Scalable Distributed Data Structures. LH* variants have been in particular developed for the high-availability files, capable of serving all the data despite unavailability of some storage sites. The scalable availability schemes, tolerating increasingly more failures when the file grows, are of particular importance. We present three high-availability LH* schemes using new concept of record grouping. We discuss the common building blocks and the specific features of each schema. We compare the design issues, properties and performance. 1