The object can move to a different remote database,
or to the local database, and the synonym name can remain the same, making access to the
object transparent to users.
How database links to remote databases are leveraged in a distributed environment is covered
further in Chapter 17.
Oracle Physical Storage Structures
The Oracle database uses a number of physical storage structures on disk to hold and manage the
data from user transactions. Some of these storage structures, such as the datafiles, redo log files,
and archived redo log files, hold actual user data; other structures, such as control files, maintain
the state of the database objects, and text-based alert and trace files contain logging information
for both routine events and error conditions in the database. Figure 1-3 shows the relationship
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Chapter 1: Getting Started with the Oracle Architecture 25
between these physical structures and the logical storage structures we reviewed in the earlier
section ???Oracle Logical Database Structures.???
Datafiles
Every Oracle database must contain at least one datafile. One Oracle datafile corresponds to one
physical operating system file on disk. Each datafile in an Oracle database is a member of one
and only one tablespace; a tablespace, however, can consist of many datafiles. (A BIGFILE
tablespace consists of exactly one datafile.)
An Oracle datafile may automatically expand when it runs out of space, if the DBA created
the datafile with the AUTOEXTEND parameter.
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