A Scheduling of Database Migration in Wide-Area Networks
Takahiro Hara, Masahiko Tsukamoto, and Shojiro Nishio
Department of Information Systems Engineering, Graduate School of Engineering, Osaka Un iversity, Suita, 565-0871
SUMMARY
In broadband networks, appropriate use of database
migration can drastically shorten the transaction processing
time of a distributed database system. So far, we have
proposed a transaction processing method based on data-
base migration, where we have assumed that the network
bandwidth is almost uniform and very broad over a whole
network. However, WANs consist of various types of net-
works such as private LANs, narrowband public networks,
and broadband backbones, and thus, it is difficult to control
database migration in the granularity of the transaction and
to execute database migration through networks other than
backbones. Therefore, the proposed method cannot be used
directly in such heterogeneous WAN environments. In this
paper, we propose a scheduling method of database migra-
tion, which gives the shortest communication time for
database operations, assuming that database migration is
used in such heterogeneous WANs. We also discuss an
implementation method of our proposed scheduling
method in a practical environment. © 2000 Scripta Tech-
nica, Syst Comp Jpn, 31(10): 1019, 2000
Key words: Database migration; WAN (wide-area
network); broadband network; distributed database.
1. Introduction
Because of the recent development of network tech-
nologies, very high speed data transmission of the order of
gigabits per second is becoming available. Since the upper
limit of the speed of light makes it impossible to improve
the propagation delay drastically, performance improve-
ments in network-wide database systems are dependent on
the effective use of broadband networks, whereas in nar-
rowband networks, the minimization of the transmitted data
volume is considered the primary factor for performance
improvement [2, 3, 11].
Here, the problem is how broadband networks can be
used effectively. A possible answer is the migration of
databases from site to site through networks. We call such
migration DB-migration. DB-migration can be performed
in a short time period in broadband networks. Therefore,
dynamic database relocation using DB-migration can be
used for several purposes, including transaction processing
[69]. In a conventional distributed database environment,
each database is fixed at a particular site, and a typical
database operation is performed through several operation
request messages. After the message exchange, the opera-
tion is validated for consistency using the two-phase com-
mit protocol (2PC). In this conventional method,
transaction processing often requires many message trans-
missions. On the other hand, if DB-migration is used, a
transaction initiation site does not need to exchange mes-
sages after it has gathered the necessary databases. The
transaction processing time is expected to be shorter than
that of the conventional database-fixed method when the
transaction is complex.
In this paper, we assume that the communication time
between the application running site and the transaction
initiation site can be negligible. In a real environment, the
application running site and the transaction initiation site
are usually different. However, they are usually close be-
cause in general, database servers are distributively located
at important points in the system and an application pro-
gram requests the transaction execution to a database server
© 2000 Scripta Technica
Systems and Computers in Japan, Vol. 31, No. 10, 2000
Translated from Denshi Joho Tsushin Gakkai Ronbunshi, Vol. J82-D-I, No. 12, December 1999, pp. 13691378
Research support: Research for the Future Program of Japan Society for
the Promotion of Science under Project Advanced Multimedia Content
Processing (JSPS-RFTF97P00501) and a Grant-in-Aid for Scientific
Research (No. 10780260) from the Ministry of Education, Science, Sports,
and Culture of Japan.
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