C. Mohan

Concurrency and recovery in generalized search trees

This paper presents general algorithms for concurrency control in tree-based access methods as well as a recovery protocol and a mechanism for ensuring repeatable read. The algorithms are developed in the context of the Generalized Search Tree (GiST) data structure, an index structure supporting an extensible set of queries and data types. Although developed in a GiST context, the algorithms are generally applicable to many tree-based access methods. The concurrency control protocol is based on an extension of the link technique originally developed for B-trees, and completely avoids holding node locks during I/Os. Repeatable read isolation is achieved with a novel combination of predicate locks and two-phase locking of data records. To our knowledge, this is the first time that isolation issues have been addressed outside the context of B-trees. A discussion of the fundamental structural differences between B-trees and more general tree structures like GiSTs explains why the algorithms developed here deviate from their B-tree counterparts. An implementation of GiSTs emulating B-trees in DB2/Common Server is underway.

Dynamic E-business: Trends in Web Services

In the last couple of years, the concept of a web service (WS) has emerged as an important paradigm for general application integration in the internet environment. More particularly, WS is viewed as an important vehicle for the creation of dynamic e-business applications and as a means for the J2EE and .NET worlds to come together. Several companies, including Microsoft, have been collaborating in proposing new WS standards. The World Wide Web Consortium has been the forum for many WS-related standardization activities. Many traditional concepts like business process management, security, directory services, routing and transactions are being extended for WS. This extended abstract traces some of the trends in the WS arena. After the TES2002 workshop is over, more information could be found in the presentation material at http://www.almaden.ibm.com/u/mohan/WebServices_TES2002_Slides.pdf

Tutorial: application servers and associated technologies

Application Servers (ASs), which have become very popular in the last few years, provide the platforms for the execution of transactional, server-side applications in the online world. ASs are the modern cousins of traditional transaction processing monitors (TPMs) like CICS. In this tutorial, I will provide an introduction to different ASs and their technologies. ASs play a central role in enabling electronic commerce in the web context. They are built on the basis of more standardized protocols and APIs than were the traditional TPMs. The emergence of Java, XML and OMG standards has played a significant role in this regard. Consequently, I will also briefly introduce the related XML, Java and OMG technologies like SOAP, J2EE and CORBA. One of the most important features of ASs is their ability to integrate the modern application environments with legacy data sources like IMS, CICS, VSAM, etc. They provide a number of connectors for this purpose, typically using asynchronous transactional messaging technologies like MQSeries and JMS. Traditional TPM-style requirements for industrial strength features like scalability, availability, reliability and high performance are equally important for ASs also. Security and authentication issues are additional important requirements in the web context. ASs support DBMSs not only as storage engines for user data but also as repositories for tracking their own state. Recently, the ECPerf benchmark has been developed via the Java Community Process to evaluate in a standardized way the cost performance of J2EE-compliant ASs. Several caching technologies have been developed to improve performance of ASs.Soon after this conference is over, the slides of this tutorial will be available on the web at the following URL: http://www.almaden.ibm.com/u/mohan/AppServersTutorial_SIGMOD2002_Slides.pdf

Application servers and associated technologies

Application Servers (ASs), which have become very popular in the last few years, provide the platforms for the execution of transactional, server-side applications in the online world. While transaction processing monitors (TPMs) have been providing similar functionality for over 3 decades, ASs are their modern equivalents. ASs play a central role in enabling electronic commerce in the web context. The objective of this seminar is to provide an introduction to different ASs and their underlying technologies for the novice as well as the experienced person. The intent is to broaden the background of database people for them to be able to better appreciate application requirements and scenarios. C. Mohan (Ph.D. 1981, UT-Austin) was named an IBM Fellow in 1997 for being recognized worldwide as a leading innovator in transaction management. He is the primary inventor of the ARIES family of recovery and locking methods, and the industry-standard Presumed Abort commit protocol. He received the 1996 ACM SIGMOD Innovations Award. At the 1999 VLDB Conference, he was honored with the 10 Year Best Paper Award for the widespread commercial and research impact of his work on ARIES. Mohan, who is an inventor of 33 patents, works very closely with numerous IBM product groups. His research results are implemented in numerous IBM and non-IBM prototypes and products like DB2, MQSeries, Lotus Domino, S/390 Parallel Sysplex and SQLServer. Currently,Mohan is a member of IBM’s Application Integration Middleware Architecture Board and is working on next generation messaging technologies and database caching in the context of WebSphere and DB2.