An example of moving a SYSAUX
occupant to a different tablespace using the command line interface can be found in Chapter 6.
FIGURE 3-1 EM Database Control SYSAUX tablespace contents
FIGURE 3-2 Using EM Database Control to move a SYSAUX occupant
Chapter 3: Planning and Managing Tablespaces 65
The SYSAUX tablespace can be monitored just like any other tablespace; later in this chapter,
we??™ll show how EM Database Control can help us to identify hotspots in a tablespace.
Undo
Multiple undo tablespaces can exist in a database, but only one undo tablespace can be active
at any given time. Undo tablespaces are used for rolling back transactions, for providing read
consistency for select statements that run concurrently with DML statements on the same table or
set of tables, and for supporting a number of Oracle Flashback features, such as Flashback Query.
The undo tablespace needs to be sized correctly to prevent ???Snapshot too old??? errors and to
provide enough space to support initialization parameters such as UNDO_RETENTION. More
information on how to monitor, size, and create undo tablespaces can be found in Chapter 7.
Temporary
More than one temporary tablespace can be online and active in the database, but until Oracle
10g, multiple sessions by the same user would use the same temporary tablespace because only
one default temporary tablespace could be assigned to a user. To solve this potential performance
bottleneck, Oracle supports temporary tablespace groups.
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