The Create Rollback Segment property sheet consists of the following pages:
â–
General (Basic UI mode)
Managing Database Storage
8-15
Rollback Segments Folder
â–
Extents (Advance UI mode)
Create Rollback Segment Property Sheet: General Page
The General page of the Create Rollback Segment property sheet is described
below:
Name
Name of the rollback segment to be created.
Enter the name of the new rollback segment. The rollback segment name can only
contain characters from your database character set and can be at most 30
characters long.
Tablespace
Name of the tablespace in which to create the rollback segment.
Choose the tablespace from the drop-down list.
Public
Toggles between public and private rollback segments. A private rollback segment
acquired explicitly by an instance when the instance opens the database. A public
rollback segment forms a pool of rollback segments that any instance requiring
rollback segments can use.
Status
Online: Specifies that the rollback segment be placed online.
Offline: Specifies that the rollback segment be place offline.
Rollback Segment Property Sheet: Extents Page
On the Extents page you can specify the storage characteristics of the rollback
segment. The Extents page contains the following fields:
Override Default Values
If this box is checked, you can edit all of the fields on the Extents page. If the box is
not checked, the default value for each field displays and the values cannot be
modified. This checkbox is only enabled during rollback Segment creation.
Initial Size
Size of the rollback segment’s first extent.
Enter the size of the initial extent. Use the unit button to specify either kilobytes or
megabytes. The default is the size of 5 data blocks.
8-16 Oracle Enterprise Manager Administrator’s Guide
Rollback Segments Folder
Next Size
Size of the next extent allocated to the rollback segment.
Enter the size of the next extent. Use the unit button to specify either kilobytes or
megabytes. The default is the size of 5 data blocks.
Optimal Size
Optimal size for the rollback segment. Optimal is not displayed for offline rollback
segments.
Enter the value for Optimal. Use the unit button to specify either kilobytes or
megabytes. Oracle tries to maintain the optimal size of the rollback segment by
dynamically deallocating extents when their data is no longer needed for active
transactions. A blank field assumes the default value.
The default value of Optimal is null. If Optimal is null, Oracle never deallocates the
rollback segment’s unused extents.
The value of Optimal can never be less than the space initially allocated to the
rollback segment, as specified by the values of Initial Extent, Next Extent, and
Minimum Extents.
Minimum Number
Total number of extents to be allocated when the rollback segment is created. This
field is only enabled when creating a rollback segment.
Enter the minimum number of extents. The default and minimum value is 2.
Maximum
Maximum number of extents that can be allocated to the rollback segment. The
default is operating system dependent.
Enter the maximum number of extents. The default and maximum values depend
on the data block size.
Altering a Rollback Segment
To alter an existing rollback segment:
1.
Select the rollback segment from the tree list. The Rollback property sheet
appears.
2.
Modify the property sheet settings as desired.
3.
Click Apply to implement the changes.
Managing Database Storage
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Rollback Segments Folder
You can also perform this operation using the Quick Edit popup menu option by
selecting the rollback segment from the multi-column list using the right mouse
button. The Quick Edit Rollback Segment property sheet is the same as the Create
Rollback Segment property sheet. See Creating a Rollback Segment on page 8-15.
Note: Any changes you make on the Storage page apply to any subsequent extent
allocations to the rollback segment, not existing extents.