This paper provides a comprehensive treatment of index management in transaction systems. We present a method, called ARIESIIM (A/gorlthm for Recovery and /so-/atIon Exploiting Semantics forlndex Management), for concurrency control and recovery of B + -trees. ARI ES/lM guarantees serializability and uses write-ahead logging for recovery. K supports very high concurrency and good performance by (1) treating as the lock of a key the same lock as the one on the corresponding record data in a data page (e.g., at the record level), (2) not acquiring, in the interest of permitting very high concurrency, commit duration locks on index pages even during index structure modification operations (SMOS) like page splits and page deletions, and (3) allowing retrievals, inserts, and deletes to go on concurrently with SMOS. During restart recovery, any necessary redos of index changes are always performed in a pageoriented fashion (i.e., without traversing the index tree) and, during normal processing and restart recovery, whenever possible undos are performed in a page-oriented fashion. ARIES/lM permits different granularities of locking to be supported in a flexible manner. A subset of ARIES/lM has been implemented in the 0S/2 Extended Edition Database Manager.1 Since the locking ideas of ARIES/lM have general applicability, some of them have also been implemented in SQUDS and the VM Shared File System, even though those systems use the shadow-page technique for recovery.

In general, performance analysis tools deal with large volumes of highly complex data of varying types and at varying levels of granularity. The result is that it is common for there to be many different tools and components that implement performance data collection, recording, and reporting in an analysis environment. This variety complicates communication within a group and makes cross-group communication about specific performance findings even more difficult. The analysis of the performance of Java TM virtual machines and Java applications introduces additional complexity. We describe an approach that unifies the recording and reporting components of performance analysis into a single data model and standard set of reports. We have employed this model with significant success in the analysis of IBM's Developer Kits for the Java virtual machine.ALEXANDER ET AL.

Performance monitor (PM) support in on-ciiipPowerPC® microprocessors is used to analyze processor, software, and system attributes for a variety of worlcloads. The interface to the PowerPC 604® microprocessor, which we abbreviate "604," has been externalized to end users. We discuss the enhanced PM support available in an upgrade of the 604, the PowerPC 604e™ microprocessor, which we abbreviate "604e." We discuss the challenges related to the externalization of the PM support as it relates to other PowerPC processors not derived from the 604 and briefly contrast these PMs with other PMs. We also describe an application programming interface (API) to the on-chip PM support, its design methodology, and its usage considerations, intended to meet these challenges.

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