In Oracle 11g, Automatic Undo Management is enabled
by default; in addition, a PL/SQL procedure is provided to help you size the UNDO tablespace.
I discuss Automatic Undo Management in detail in Chapter 7.
Oracle Logical Database Structures
In this section, we will cover the highlights of all major logical database structures, starting with
tables and indexes. Next, we discuss the variety of datatypes we can use to define the columns of
a table. When we create a table with columns, we can place restrictions, or constraints, on the
columns of the table.
One of the many reasons we use a relational database management system (RDBMS) to
manage our data is to leverage the security and auditing features of the Oracle database. We will
review the ways we can segregate access to the database by user or by the object being accessed.
We??™ll also touch upon many other logical structures that can be defined by either the DBA or
the user, including synonyms, links to external files, and links to other databases.
Tables
A table is the basic unit of storage in an Oracle database. Without any tables, a database has
no value to an enterprise. Regardless of the type of table, data in a table is stored in rows and
columns, similar to how data is stored in a spreadsheet. But that is where the similarity ends.
The robustness of a database table due to the surrounding reliability, integrity, and scalability
of the Oracle database makes a spreadsheet a poor second choice when deciding on a place
to store critical information.
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