Information Technology Reference
In-Depth Information
In a transaction-server system, almost all of the functionality of database
management and transaction processing resides at the server, while in a data-server
system, much of the functionality is included in the local systems running at the
clients. In a page server, and especially in a file server, the functionality of the
database server is most stripped down: from the point of view of the database server
in a page-server or file-server system, the database is (almost) only a collection of
pages or files whose shared use and persistence are managed by the server. The local
systems running at the clients are aware of the structure of the logical database and
index structures and access paths to the relations or object collections.
Computer-aided design and manufacturing applications (
CAD
,
CAM
) running
on powerful workstations are often built on an object-oriented database system
organized as a data-server system. With a data-server system, the computing
resources of workstations are more effectively used than with a transaction-server
system.
14.2
Page-Server Architecture
A page-server system consists of a database server s and a set of client machines or
workstations c
1
;:::;c
n
, connected to the server machine via a network (Fig.
14.1
).
At the server, there are the disk drives that store the disk version of the database and
the log disk that stores the log file. The clients do not store permanently any part
of the database or the log. The server buffer is used to buffer pages fetched from
disk and updated pages shipped from the clients. The private client buffers (or client
caches) are used to buffer pages shipped from the server.
Fig. 14.1
Page-server architecture
