Autonomes Index Tuning - DBMS-integrierte Verwaltung von Soft Indexen
Das Self Management in DBMS, und das Self Tuning als wichtiger Teil davon, gewinnt auf Grund der wachsenden Komplexitat von Systemen und Anwendungen und den daraus resultierenden steigenden Betriebskosten zunehmend an Beachtung. Der Stand der Technik bezuglich des Index Tunings sind AdministrationsTools, die aus einem gegebenen Workload eine empfohlene Indexkonfiguration ableiten. Diese muss jedoch bei Anderungen des Systems, dessen Umgebung oder der Zugriffsmuster wiederholt angepasst werden. Wir stellen in diesem Beitrag einen dynamischen Ansatz zum Index Tuning vor, der zur Laufzeit das Systemverhalten und die -nutzung uberwacht, Entscheidungen bezuglich moglicher Verbesserungen der aktuellen Indexkonfiguration trifft und diese integriert mit der Anfrageverarbeitung umsetzt. Fur den zuletzt genannten Aspekt fuhren wir mit IndexBuildScan und SwitchPlan neue Operatoren zur Erzeugung von Indexen wahrend der Bearbeitung einer Anfrage sowie deren sofortiger Nutzung ein. Die Beschreibung der Implementierung der vorgestellten Konzepte als Erweiterung des PostgreSQL-Systems, sowie eine Evaluierung an Hand eines von TPC-H abgeleiteten Benchmarks beschliesen den Beitrag.

title: Green Computing - A Case for Data Caching and Flash Disks?
abstract: Green computing or energy saving when processing information is primarily considered a task of processor development. However, this position paper advocates that a holistic approach is necessary to reduce power consumption to a minimum. We discuss the potential of integrating NAND flash memory into DB-based architectures and its support by adjusted DBMS algorithms governing IO processing. The goal is to drastically improve energy efficiency while comparable performance as is disk-based systems is maintained.

title: Autonomous Management of Soft Indexes
abstract: In recent years the support for index tuning as pan of physical database design has gained focus in research and product development, which resulted in index and design advisors. Nevertheless, these tools provide a one-off solution for a continuous task and are not deeply integrated with the DBMS functionality by only applying the query optimizer for index recommendation and profit estimation and decoupling the decision about and execution of index configuration changes from the core system functionality. In this paper we propose an approach that continuously collects statistics for recommended indexes and based on this, repetitively solves the Index Selection Problem (lSP).A key novelty is the on-the-fly index generation during query processing implemented by new query plan operators In-dexBuildScan and SwitchPlan. Finally, we present the implementation and evaluation of the introduced concepts as part of the PostgreSQL system.

title: Essential Performance Drivers in Native XML DBMSs
abstract: As a multi-layered XML database management system, we have designed, implemented, and optimized over the recent five years our prototype system XTC, a native XDBMS providing multi-lingual query interfaces (XQuery, XPath, DOM). In particular in higher system layers, we have compared competing concepts and iteratively found salient solutions which drastically improved the overall XDBMS performance. XML query processing is critically affected by the smooth interplay of concepts and methods on all architectural layers: node labeling and mapping options for storage structures; availability of suitable index mechanisms; provision of a spectrum of path processing operators; query language compilation and optimization. Furthermore, effective and efficient locking protocols must be present to guarantee the ACID properties for XML processing and to achieve high transaction throughput. 
 
In this survey, we outline our experiences gained during the implementation and optimization of XTC. We figure out the "key drivers" to maximize throughput while keeping the response times at an acceptable level. Because we have implemented all options and alternatives in XTC, dedicated benchmark runs allow for comparisons in identical environments and illustrate the benefit of all implementation decisions.

title: The promise of solid state disks: increasing efficiency and reducing cost of DBMS processing
abstract: Most database systems (DBMSs) today are operating on servers equipped with magnetic disks. In our contribution, we want to motivate the use of two emerging and striking technologies, namely native XML DBMSs (XDBMSs for short) and solid state disks. In this context, the traditional read/write model optimized by a sophisticated cache hierarchy and the IO cost model for databases needs adjustment. Such new devices together with optimized storage mapping of XML documents provide a number of challenging characteristics. We discuss howtheir optimization potential ca be exploited to enhance transactional DB performance under reduced energy consumption to match increasing application demands and, at the same time, to guarantee economic energy use in data centers.

title: Usage-driven storage structures for native XML databases
abstract: There are numerous and influential parameters associated with the selection of suitable native storage structures for XML documents within an XML DBMS. The most important parameters are related to node labeling, path synopsis, document container layout, indexing, and text compression. While node labeling and the presence of a path synopsis greatly determine flexibility and efficiency of the entire DBMS-internal XML processing, the remaining issues primarily address I/O demand and space consumption. In particular, text compression---considered orthogonal to the design choices affected by the other parameters---implies additional algorithmic costs for encoding/decoding during document processing. Having the vision in mind that future storage managers can autonomously figure out optimal choices for all of these parameters, we discuss how various storage options favor different usage patterns and how they can be specified beforehand to influence native XML storage options by the anticipated usages.

title: Controllability of Open Workflow Nets.
abstract: An open workflow net is basically a workflow net extended with a message passing interface. Open workflow nets are adequate models for services or parts of inter-organizational business processes. We investigate the problem of controllability, a natural counterpart of soundness in classical workflow nets (as studied by van der Aalst). We distinguish centralized, distributed, and local controllability and provide solutions to all problems.

title: Stubborn Sets for Standard Properties
abstract: Stubborn sets are a tool for state space reduction preserving certain system properties. We present stubborn set approaches for all popular Petri net standard properties. This extends the list of properties that can be analysed successfully (including boundedness, reversibility). For other properties, our approach can lead to larger reductions (reachability) than previous ones. Furthermore, shortest and chepest witness paths for several properties are now preserved.

title: LoLA wird Pfadfinder.
abstract: LoLA ist ein erreichbarkeitsgraphbasiertes Werkzeug f ur Stellen/Transitions{Netze. Hier geht es um LoLAs Fahigkeit, erreichbare Zustande mit vorgegebenen Eigenschaften zu suchen und im Erfolgsfall einen solchen Zustand mit einem Weg von der Anfangsmarkierung dorthin anzugeben. Die Besonderheit besteht darin, da wahrend der Suche nur zwei Zustande gespeichert werden: der Anfangszustand und der aktuelle Zustand. Anstatt also den Zustandsraum systematisch zu durchmustern (und dabei meist am Speicherende zu scheitern), navigiert LoLA ohne Kenntnis der schon betretenen Zustande durch den Erreichbarkeitsgraph. Da sie trotzdem ihre Aufgabe erfolgreich lost, liegt an ihren spezi schen Fahigkeiten: Schnelligkeit, Bescheidenheit, Zielstrebigkeit, Neugier und Ausdauer.

title: How to calculate symmetries of Petri nets
abstract: Symmetric net structure yields symmetric net behaviour. Thus, knowing the symmetries of a net, redundant calculations can be skipped. We present a framework for the calculation of symmetries for several net classes including place/transition nets, timed nets, stochastic nets, self–modifying nets, nets with inhibitor arcs, and many others. Our approach allows the specification of different symmetry groups. Additionally it provides facilities either to calculate symmetries on demand while running the actual analysis algorithm, or to calculate them in advance. For the latter case we define and calculate a ground set of symmetries. Such a set has polynomial size and is sufficient for an efficient implementation of the for all symmetries loop and the partition of net elements into equivalence classes. These two constructions are the usual way to integrate symmetries into an analysis algorithm.

title: Model-Checking with Coverability Graphs
abstract: We show that several formulas of a temporal logic can be verified using the coverability graph of the underlying system. Of course, the procedure is not capable of verifying all formulae, since already the reachability problem for (unbounded) Petri nets is computationally hard. Thus, the procedure returns true, false, or unknown for a query. The formulae that can be verified cover most of the well known standard properties which have been listed in the context of coverability graph analysis so far.