Database Reference
In-Depth Information
3.3
Oracle Database Physical Architecture
Let's break the physical and logical layers into sections:
Where and how is data stored? In datafiles, tablespaces, and objects.
What about recoverability? Controlfiles, logging, and archiving are
used.
How are changes undone? Rollback or undo spaces allow undoing of
changes.
How are large sorts handled? Specially formatted files are used for fast
on-disk sorting.
Each of these areas is discussed in the following sections.
3.3.1
Datafiles, Tablespaces, and Objects
Figure 3.9 shows the internal physical structure of an Oracle database,
showing the way in which data is stored.
Tablespaces
are logical structural
overlays containing one or more datafiles. A
(owner or Oracle user)
is also a logical overlay structure. A schema can be spread across multiple
tablespaces and contains segments or database objects such as rollback seg-
ments, temporary segments or tables, and indexes.
schema
are physical or
logical subdivisions within schemas and can be accessed across different
Segments
Figure 3.9
Database Physical
Structure.
