Multi-level Garbage Collection in a High-Performance Persistent Object System

Wolczko, Mario; Williams, I.

doi:10.1007/978-1-4471-3209-7_23

Cited by 8 publications

(3 citation statements)

References 16 publications

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“…One of the possible roles of a unique index, besides efficient access and enforcement of uniqueness, is service as a logical-to-physical mapping table [Martin 1975, pp. 357-359;Wolczko and Williams 1992;Srinivasan et al 2000]. For parallel or distributed data, if several nodes each have a copy of the mapping table, and the table is updated at one node, then the updates must eventually propagate to the other copies [Vingralek et al 1994;1998].…”

Section: References To Data That Has Movedmentioning

confidence: 99%

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Online reorganization of databases

Sockut

Iyer

2009

ACM Comput. Surv.

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In practice, any database management system sometimes needs reorganization, that is, a change in some aspect of the logical and/or physical arrangement of a database. In traditional practice, many types of reorganization have required denying access to a database (taking the database offline) during reorganization. Taking a database offline can be unacceptable for a highly available (24-hour) database, for example, a database serving electronic commerce or armed forces, or for a very large database. A solution is to reorganize online (concurrently with usage of the database, incrementally during users' activities, or interpretively). This article is a tutorial and survey on requirements, issues, and strategies for online reorganization. It analyzes the issues and then presents the strategies, which use the issues. The issues, most of which involve design trade-offs, include use of partitions, the locus of control for the process that reorganizes (a background process or users' activities), reorganization by copying to newly allocated storage (as opposed to reorganizing in place), use of differential files, references to data that has moved, performance, and activation of reorganization. The article surveys online strategies in three categories of reorganization. The first category, maintenance, involves restoring the physical arrangement of data instances without changing the database definition. This category includes restoration of clustering, reorganization of an index, rebalancing of parallel or distributed data, garbage collection for persistent storage, and cleaning (reclamation of space) in a logstructured file system. The second category involves changing the physical database definition; topics include construction of indexes, conversion between B + -trees and linear hash files, and redefinition (e.g., splitting) of partitions. The third category involves changing the logical database definition. Some examples are changing a column's data type, changing the inheritance hierarchy of object classes, and changing a relationship from one-to-many to many-to-many. The survey encompasses both research and commercial implementations, and this article points out several open research topics. As highly available or very large databases continue to become more common and more important in the world economy, the importance of online reorganization is likely to continue growing.

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Section: References To Data That Has Movedmentioning

confidence: 99%

“…The strategy of Wolczko and Williams [1992] applies to a persistent object system that has three levels of storage: cache, main storage, and disk. All creation of objects takes place in the cache.…”

Section: Wolczko and Williamsmentioning

confidence: 99%

Online reorganization of databases

Sockut

Iyer

2009

ACM Comput. Surv.

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“…This normally means organising data around fixedlength 'pages', and then using object clustering to achieve adequate performance. See [9] and [21].…”

Section: Can Pages Be Used As the Intermediate Structure?mentioning

confidence: 99%

The case for segments

Cooper

Wise

Proceedings of International Workshop on Object Orientation in Operating Systems

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This paper argues two points: firstly that persistent systems ought to have some kind of user-level intermediate structure, unlike systems where the persistent store is just a huge collection of small objects; and secondly it describes the Barbados system (which has such an intermediate structure) and argues that it is an effective implementation of persistence.The argument is that many operations have high fixed overhead costs, but that these costs can be factored out by grouping small objects together and operating on them as a group.These 'operations' include both implementation-level and user-level operations, for example transferral of data-structures to remote systems. Therefore, the 'loss of orthogonality', or the fact that the programmer now has to deal with these storage entities is not a compromise that is being made, but rather a conceptual advance that is to be em braced ( !).The Barbados system, which has been implemented, is based on the idea of a 'segment'. A segment is a grouping of logically related small objects that acts as a coherent (medium-sized) object. It can also be thought of as a 'data-structure'. These entities are simultaneously the units of disk i/o, sharing, locking, storage, memory protection, recompilation, persistence, transferral, deletion and so on.The first point is almost a philosophical point.

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The Influence of the Object-Oriented Language Model on a Supporting Architecture

Wolczko

Williams

1994

The Interaction of Compilation Technology and Computer Architecture

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Multi-level Garbage Collection in a High-Performance Persistent Object System

Cited by 8 publications

References 16 publications

Online reorganization of databases

Online reorganization of databases

The case for segments

The Influence of the Object-Oriented Language Model on a Supporting Architecture

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