|Lesson 7 ||Temporary LOBs|
|Objective||Understand how and why to use temporary LOBs |
How and why to use Temporary LOBs
A temporary LOB is a way to store a LOB in a temporary tablespace. These
temporary LOBs, by default, last only for the duration of a session. You would typically use a temporary LOB when you are performing a number of operations on a LOB (such as morphing an image) and you want to keep a complete copy of the LOB temporarily.
How to use temporary LOB
You create and manipulate temporary LOBs with procedures from the
DBMS_LOB package. These procedures are as follows:
| Procedure ||Description |
|This procedure creates a temporary LOB. You can specify whether you want a temporary LOB to last for the duration of the session or the duration of the particular call. |
| code>DBMS_LOB.FREETEMPORARY || This procedure frees the space used by a temporary LOB and invalidates the LOB locator for the temporary LOB. |
|This procedure checks to see if a particular LOB is a temporary or permanent LOB.|
When you create a temporary LOB, it is empty. You can use the
DBMS_LOB.COPY() function to move the contents of a permanent LOB into a temporary LOB. The specific temporary LOB operations are illustrated in the following Slide Show:
Create Temporary Lobs
You can also use most of the manipulation functions in the
DBMS_LOB package on temporary LOBs.
Once a temporary LOB is created, you can use it as a value in a
WHERE clause for
DELETE statements, or as a location to
If you select into a temporary LOB from a permanent LOB, the LOB locator for the permanent LOB overwrites the temporary LOB locator, rather than copying the value of the permanent LOB into the temporary LOB.
In the next lesson, you will learn about buffering options for LOBs.