All these Flashback
options are covered in more detail at the end of this chapter.
Managing Undo Tablespaces
Creating and maintaining undo tablespaces is a ???set it and forget it??? operation once the undo
requirements of the database are understood. Within the undo tablespace, Oracle automatically
creates, sizes, and manages the undo segments, unlike previous versions of Oracle in which the
DBA would have to manually size and constantly monitor rollback segments.
In the next couple sections, we??™ll review the processes used to create and manage undo
tablespaces, including the relevant initialization parameters. In addition, we??™ll review some
scenarios where we may create more than one undo tablespace and how to switch between
undo tablespaces.
Creating Undo Tablespaces
Undo tablespaces can be created in two ways: at database creation or with the create tablespace
command after the database is created. As with any other tablespace in Oracle 10g, the undo
tablespace can be a bigfile tablespace, further easing the maintenance of undo tablespaces.
Creating an Undo Tablespace with CREATE DATABASE
A database may have more than one undo tablespace, although only one can be active at a time.
Here??™s what creating an undo tablespace at database creation looks like:
Chapter 7: Managing Transactions with Undo Tablespaces 211
create database ord
user sys identified by ds88dkw2
user system identified by md78s233
sysaux datafile '/u02/oradata/ord/sysaux001.
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