Database Reference
In-Depth Information
After having this concept, I would like to define the relationship
between logical and physical architecture of Oracle Database in
the following lines. It's very important and I want you to
memorize it word by word. First understand it then memorize it.
Each tablespace can have one or more data files associated with
it but each data file can never belong to more than one
tablespace.
Segments (database objects) can lie in more than one data file
within the table space. This can be better visualized by looking at
the next Figure 3-7. Whenever you create a database object,
Oracle Instance allocates a segment in the tablespace assigned to
your schema.
With the Figure 3-7, you can easily visualize the physical and
logical architecture of Oracle Database. For some people this
figure would be self-explanatory and how truly someone has
said, “A Picture is better than thousand words”. As shown in the
Figure 3-7, this Oracle Database is comprised of two tablespaces
namely Tablespace 1 and Tablespace 2. Tablespace 1 is
comprised of two data files whereas Tablespace 2 is comprised
of one data files. So we can say that this oracle database has
three data files.
Tablespace 1 has total of six segments or database objects
(tables, views, synonym etc.) and some segments are totally
residing in one data file whereas some are residing partially in
one data file and partially in other data file e.g. keep in focus
Tablespace 1, the data inside segment 2 (SG 2) and segment 5
(SG 5) is distributed among two data files.
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