A multidimensional and multiversion structure for OLAP applications

When changes occur on data organization, conventional multidimensional structures are not adapted because dimensions are supposed to be static. In many cases, especially when time covered by the data warehouse is large, dimensions of the hypercube must be redesigned in order to integrate evolutions. We propose an approach allowing to track history but also to compare data, mapped into static structures. We define a conceptual model building a Mutiversion Fact Table from the Temporal Multidimensional Schema and we introduce the notion of temporal modes of representation corresponding to different ways to analyze data and their evolution

Report on the 6th ADBIS’2002 conference

The 6th East European Conference ADBIS 2002 was held on September~8--11, 2002 in Bratislava, Slovakia. It was organised by the Slovak University of Technology (and, in particular, its Faculty of Electrical Engineering and Information Technology) in Bratislava in co-operation with the ACM SIGMOD, the Moscow ACM SIGMOD Chapter, and Slovak Society for Computer Science. The call for papers attracted 115 submissions from 35~countries. The international program committee, consisting of 43 researchers from 21 countries, selected 25 full papers and 4 short papers for a monograph volume published by the Springer Verlag. Beside those 29 regular papers, the volume includes also 3 invited papers presented at the Conference as invited lectures. Additionally, 20 papers have been selected for the Research communications volume. The authors of accepted papers come from 22~countries of 4 continents, indicating the truly international recognition of the ADBIS conference series. The conference had 104 registered participants from 22~countries and included invited lectures, tutorials, and regular sessions. This report describes the goals of the conference and summarizes the issues discussed during the sessions

Creation and management of versions in multiversion data warehouse

ABSTRACT A data warehouse (DW) provides an information for analytical processing, decision making, and data mining tools. On the one hand, the structure and content of a data warehouse reflects a real world, i.e. data stored in a DW come from real production systems. On the other hand, a DW and its tools may be used for predicting trends and simulating a virtual business scenarios. This activity is often called the what-if analysis. Traditional DW systems have static structure of their schemas and relationships between data, and therefore they are not able to support any dynamics in their structure and content. For these purposes, multiversion data warehouses seem to be very promising. In this paper we present a concept and an ongoing implementation of a multiversion data warehouse that is capable of handling changes in the structure of its schema as well as simulating alternative business scenarios

A Comparative Study: Change Detection and Querying Dynamic XML Documents

The efficient management of the dynamic XML documents is a complex area of research. The changes and size of the XML documents throughout its lifetime are limitless. Change detection is an important part of version management to identify difference between successive versions of a document. Document content is continuously evolving. Users wanted to be able to query previous versions, query changes in documents, as well as to retrieve a particular document version efficiently. In this paper we provide comprehensive comparative analysis of various control schemes for change detection and querying dynamic XML documents

Serializable Isolation for Snapshot Databases

Many popular database management systems implement a multiversion concurrency control algorithm called snapshot isolation rather than providing full serializability based on locking. There are well-known anomalies permitted by snapshot isolation that can lead to violations of data consistency by interleaving transactions that would maintain consistency if run serially. Until now, the only way to prevent these anomalies was to modify the applications by introducing explicit locking or artificial update conflicts, following careful analysis of conflicts between all pairs of transactions. This thesis describes a modification to the concurrency control algorithm of a database management system that automatically detects and prevents snapshot isolation anomalies at runtime for arbitrary applications, thus providing serializable isolation. The new algorithm preserves the properties that make snapshot isolation attractive, including that readers do not block writers and vice versa. An implementation of the algorithm in a relational database management system is described, along with a benchmark and performance study, showing that the throughput approaches that of snapshot isolation in most cases

A Strategy for Reducing I/O and Improving Query Processing Time in an Oracle Data Warehouse Environment

In the current information age as the saying goes, time is money. For the modern information worker, decisions must often be made quickly. Every extra minute spent waiting for critical data could mean the difference between financial gain and financial ruin. Despite the importance of timely data retrieval, many organizations lack even a basic strategy for improving the performance of their data warehouse based reporting systems. This project explores the idea that a strategy making use of three database performance improvement techniques can reduce I/O (input/output operations) and improve query processing time in an information system designed for reporting. To demonstrate that these performance improvement goals can be achieved, queries were run on ordinary tables and then on tables utilizing the performance improvement techniques. The I/O statistics and processing times for the queries were compared to measure the amount of performance improvement. The measurements were also used to explain how these techniques may be more or less effective under certain circumstances, such as when a particular type of query is run. The collected I/O and time based measurements showed a varying degree of improvement for each technique based on the query used. A need to match the types of queries commonly run on the system to the performance improvement technique being implemented was found to be an important consideration. The results indicated that in a reporting environment these performance improvement techniques have the potential to reduce I/O and improve query performance

Fast transactions for multicore in-memory databases

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 55-57).Though modern multicore machines have sufficient RAM and processors to manage very large in-memory databases, it is not clear what the best strategy for dividing work among cores is. Should each core handle a data partition, avoiding the overhead of concurrency control for most transactions (at the cost of increasing it for cross-partition transactions)? Or should cores access a shared data structure instead? We investigate this question in the context of a fast in-memory database. We describe a new transactionally consistent database storage engine called MAFLINGO. Its cache-centered data structure design provides excellent base key-value store performance, to which we add a new, cache-friendly serializable protocol and support for running large, read-only transactions on a recent snapshot. On a key-value workload, the resulting system introduces negligible performance overhead as compared to a version of our system with transactional support stripped out, while achieving linear scalability versus the number of cores. It also exhibits linear scalability on TPC-C, a popular transactional benchmark. In addition, we show that a partitioning-based approach ceases to be beneficial if the database cannot be partitioned such that only a small fraction of transactions access multiple partitions, making our shared-everything approach more relevant. Finally, based on a survey of results from the literature, we argue that our implementation substantially outperforms previous main-memory databases on TPC-C benchmarks.by Stephen Lyle Tu.S.M