Database Reference
In-Depth Information
master database and a replica in a process called synchronization. For example, after the second user returns
from the remote site, the DBA synchronizes the master database and the
as shown in
Figure 7-18. Later, after the first user returns, the DBA synchronizes the master database and the
“
Replica 2 database,
”
“
Replica 1
database.
”
Master
database
Replica 2
database
DBMS
252
DBMS exchanges the
updated data between
the two databases
FIGURE 7-18
DBMS synchronizes two databases in a replica set
Ideally, the DBMS should handle all the issues associated with replication for you. The DBMS should do
all the work to keep the various copies of data consistent behind the scenes; users should be unaware of the
work involved. You
'
ll learn more about replication in Chapter 9.
PROVIDE UTILITY SERVICES
A DBMS must provide services that assist in the general maintenance of a database. In addition to the ser-
vices already discussed, a DBMS provides a number of utility services that assist in the general maintenance
of the database. The following is a list of services that might be provided by a PC-based DBMS:
The DBMS lets you change the database structure
adding new tables and fields, deleting exist-
ing tables and fields, changing the name or properties of fields, and so on.
—
The DBMS lets you add new indexes and delete indexes that are no longer needed.
While you are using the database, the DBMS lets you use the services available from your oper-
ating system, such as Windows or Linux.
The DBMS lets you export data to and import data from other software products. For example,
you can transfer data easily between the DBMS and a spreadsheet file, a word-processing file, a
graphics program file, or even another DBMS.
The DBMS provides support for easy-to-use edit and query capabilities, screen generators, report
generators, and so on.
The DBMS provides support for both procedural and nonprocedural languages. With a proce-
dural language, you must tell the computer precisely how a given task is to be accomplished;
Basic, C++, and COBOL are examples of procedural languages. With a nonprocedural language,
you merely describe the task you want the computer to accomplish. The nonprocedural language
then determines how the computer will accomplish the task. SQL is an example of a nonproce-
dural language.
The DBMS provides an easy-to-use, menu-driven interface that allows users to tap into the power
of the DBMS without having to learn a complicated set of commands.
