Improving performance for LOB data
You can improve the performance of applications that access LOB data by specifying that an inline portion of LOB data columns be stored in the base table space along with data from the other non-LOB columns.
About this task
An inline LOB allows a portion of LOB data to reside in the base table space with the data from non-LOB columns. For LOBs of a size less than or equal to the specified inline length, Db2 stores the complete LOB data in the base table space. Db2 does not need to access the LOB table space or auxiliary indexes for processes that access the LOB data.
In such cases, Db2 can access the data at similar cost, in terms of CPU time and elapsed time, for comparable non-LOB data types. The amount of disk space that is used for LOB data is also reduced when the LOB data can be stored inline in the base table space.
For LOBs of a size greater than the specified inline length, the inline portion of the LOB resides in the base table space, and Db2 stores the remainder of the LOB in the LOB table space. In this case, any process that accesses the LOB data must access both the base table space and the LOB table space.
The benefits of inline LOBs are greatest for frequently accessed LOB columns. For LOB column that are accessed only rarely, the presence of the inline LOB data in the base table might reduce the number of row-per-page enough to incur increased I/O costs that outweigh any benefits of keeping the LOB data inline.
Procedure
To specify a length for inline LOBs, use the following approaches: