Information Technology Reference
In-Depth Information
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Database
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Data
Figure1.7: Database
simultaneously accessed by many different users in many different loca-
tions. Databases therefore need to allocate resources among different user
requests, isolate concurrent updates to shared data, and ensure data is
stored consistently on disk. In fact, several of the file system storage tech-
niques we will discuss for operating systems, were originally developed for
database systems.
{ Referee. How should resources be allocated among the various users
of a database? How does the database enforce data privacy so that
only authorized users access relevant data?
{ Illusionist. How does the database mask machine failures so that
data is always stored consistently regardless of when the failure oc-
curs?
{ Glue. What common services make it easier for database users to
develop their programs?
Parallel applications (Figure 1.8) are programs that have been designed
to take advantage of multiple processors on a single computer. Each appli-
cation multiplexes its work onto a fixed number of processors and needs to
ensure that accesses to shared data structures are coordinated to preserve
consistency. While some parallel programs directly use the services pro-
