VAGABOND - The Design and Analysis of a
Temporal Object Database Management System
Kjetil Nørvåg
Department of Computer and Information Science
Norwegian University of Science and Technology
7491 Trondheim, Norway
noervaag at idi.ntnu.no
Abstract
Storage costs are rapidly decreasing, making it feasible to store
larger amounts of data in databases. However, the increase in disk
performance is much lower than the increase in memory and CPU
performance, and we have an increasing secondary storage access
bottleneck. Even though this is not a new situation, the advent of
very large main memory has made new storage approaches possible.
In most current database systems, data is updated in-place. To support
recovery and increase performance, write-ahead logging is used. This
logging defers the in-place updates. However, sooner or later, the
updates have to be applied to the database. This often results in
non-sequential writing of lots of pages, creating a write
bottleneck. To avoid this, another approach is to eliminate the
database completely, and use a log-only approach, similar to the
approach used in log structured file systems. The log is written
contiguously to the disk, in a no-overwrite way, in large blocks.
This thesis presents the architecture and design of Vagabond, a
temporal object database management system (ODBMS) based on
the log-only principle. Solutions to problems regarding temporal data
management, fast recovery, efficient management of large objects,
dynamic reclustering, and dynamic tuning of system parameters are provided. This includes a new index structure for
indexing temporal objects, persistent caching of index entries to
solve the object indexing bottleneck, algorithms for transaction
management, and declustering strategies to be used in a parallel
temporal ODBMS.
In order to compare the log-only approach with the traditional
in-place update approach, analytical cost models are used to study
the performance of the approaches. The analysis shows that with the
workloads we expect to be typical for future ODBMSs, the log-only
approach is highly competitive with the traditional in-place update
approach.
Many of the ideas presented in this thesis are also useful outside the
log-only context. In papers included as appendixes, we
show how the ideas can be applied to temporal ODBMSs based on
traditional in-place updating techniques.
The whole thesis is available as postscript, gzip'ed postscript, and pdf.
Last modified: Fri May 24 19:05:20 MEST 2002