SQL> select ts.name ts_name, df.name df_name, bytes
2 from v$tablespace ts join v$datafile df using(ts#)
3 where ts.name = 'UNDO_BI';
TS_NAME DF_NAME BYTES
------------ --------------------------------------------- ----------
UNDO_BI +DATA/dw/datafile/undo_bi.275.629807457 104857600
SQL>
Because we did not specify a datafile size either, the tablespace defaults to a size of 100MB;
in addition, the datafile is autoextensible with an unlimited maximum size, limited only by the file
system.
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216 Oracle Database 11g DBA Handbook
Undo Tablespace Dynamic Performance Views
A number of dynamic performance views and data dictionary views contain information about
undo tablespaces, user transactions, and undo segments. Table 7-1 contains the view names and
their descriptions.
The views in Table 7-1 are described in more detail later in this chapter.
Undo Tablespace Initialization Parameters
In the following sections, we??™ll describe the initialization parameters needed to specify the undo
tablespace for the database as well as control how long Oracle will retain undo information in
the database.
UNDO_MANAGEMENT
The parameter UNDO_MANAGEMENT defaults to MANUAL in Oracle Database 10g, and AUTO
in Oracle Database 11g. Setting the parameter UNDO_MANAGEMENT to AUTO places the
database in Automatic Undo Management mode. At least one undo tablespace must exist in the
database for this parameter to be valid, whether UNDO_TABLESPACE is specified or not.
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