Space Analyst for Oracle - Tablespace Map Tab
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The Tablespace Map tab lets you view a graphical layout regarding the physical placement of every object inside a selected tablespace. The tablespace map also helps identify fragmentation problems for a tablespace (honeycomb and bubble). An object grid is also present that lets you view detailed information about every object's storage properties.
The Space Info section contains information regarding the total, used, and free space (in MB) for the tablespace.
The View By section allows you to switch between two different tablespace map views:
| Option | Description |
|---|---|
|
Object Type |
The normal tablespace map mode, which is color-coded by object type. Pressing the legend button shows the various colors assigned to the object types contained within the tablespace. |
|
Extent Problems |
When in this mode, the tablespace map highlights in red any object containing one or both of these object extent problems:· - Max extent problem - the object has reached or is near its maximum extent limit. - Extent deficit - the object may not be able to allocate its next extent because the tablespace does not currently have enough contiguous free space. This problem will be highlighted even if the tablespace has its autoextend property for one or more datafiles set to true. |
When in Object Type mode, the accompanying grid of the tablespace map contains the following data:
| Data | Description |
|---|---|
|
Name |
The name of the object in owner.object name.partition name format. |
|
Extents |
The total number of allocated extents for the object. |
|
Blocks |
The total number of allocated blocks for the object. |
|
Bytes |
The total number of allocated bytes for the object. |
|
Type |
The object type (table, index, etc.) |
|
Initial Extent |
The initial space extent (in bytes) allocated to the object. |
|
Next Extent |
The next extent (in bytes) that the object will attempt to allocate when more space for the object is required. |
|
Percent Increase |
The percent increase property for the object. |
When in Extent Problems mode, the accompanying grid of the tablespace map contains the following data:
| Data | Description |
|---|---|
|
Name |
The name of the object in owner.object name.partition name format. |
|
Extents |
The total number of allocated extents for the object. |
|
Blocks |
The total number of allocated blocks for the object. |
|
Bytes |
The total number of allocated bytes for the object. |
|
Type |
The object type (table, index, etc.) |
|
Initial Extent |
The initial space extent (in bytes) allocated to the object. |
|
Next Extent |
The next extent (in bytes) that the object will attempt to allocate when more space for the object is required. |
|
Percent Increase |
The percent increase property for the object. |
|
Max Extent Percent |
A percentage indicating how close the object is to reaching its maximum extent limit. For example, a 100 indicates an object that has reached its maximum extent limit. |
|
Extendibility |
Indicates if the object can allocate its next extent. If 'N', this is because the tablespace does not currently have enough contiguous free space. This problem will be highlighted even if the tablespace has its autoextend property for one or more datafiles set to true. |
When viewing a tablespace in the graphical map, there are two broad categories of fragmentation that you will want to be on the lookout for: free space honeycombs and free space bubbles. Honeycomb fragmentation is really not difficult to detect or handle and occurs when two free space extents in a tablespace reside next to one another. For example, rather than having one large free space extent of 6MB, a tablespace might have two extents that are next to each other (a honeycomb) that make up 3MB and 3MB. If an incoming object required a single 4MB extent allocation, Oracle would have to coalesce the honeycomb to make room for the object. The necessary coalesce operation would cause a small degree of performance degradation, however the situation would be resolved and no space-related bottleneck would remain.
Fragmentation bubbles, however, are another story and are the traditional reason DBAs have had to perform full tablespace reorganizations. Bubbles occur when objects are continuously added and dropped in a tablespace, with the end result being free space pockets (or bubbles) being interspersed between objects that remain in the tablespace. This can become problematic when, for example, an incoming object requires a single 5MB extent allocation, but there is not enough contiguous space in the tablespace to meet the demand. Even if the total amount of free space in the tablespace equals the required 5MB, it will do no good if that 5MB is made up of 5 non-contiguous blocks of free space. In this situation, Oracle has no alternative but to either extend the datafile to make room for the object (if the tablespace's datafile has the AUTOEXTEND property enabled), or return an error and deny the object entry into the tablespace.
Space Analyst makes it easy to recognize both of these bottleneck headaches. When the map is viewed in Object Type mode, pockets of green seen throughout the tablespace indicate bubble fragmentation, while two or more blocks of green segments viewed next to one another in the map indicate honeycomb fragmentation.
The Tablespace Map tab includes the following buttons:
| Button | Description |
|---|---|
|
Legend |
Opens the Tablespace Map Legend. |
|
Display |
Opens the Display window. The Display window lets you specifies the magnification level for the Tablespace Map. |
|
Fit to Window |
Fits the Tablespace Map to the window. |
|
Full Screen |
Fits the Tablespace Map to the full screen. |
|
Print Map |
Opens the Print dialog to print the Tablespace Map. |
Available Functionality
The following functionality is available in the Command menu, shortcut menu, and toolbar:
- Analysis Report
- Convert to Dictionary-Managed
- Convert to Locally-Managed
- Estimate Size
- Extract
- Open Wizard
- Reorganize
- Update Statistics
- Tablespaces Wizard (DB2 LUW)
- Threshold Options