Choosing data page sizes for LOB data
Choosing a data page size for LOBs (in the LOB table space) is a trade-off between minimizing the number of getpage operations (maximizing performance) and not wasting space.
About this task
With LOB table spaces, no more than one LOB value is ever stored in any single data page in a LOB table space. Space that is not used by the LOB value in the last page that is occupied by the LOB remains unused. DB2® also uses additional space for control information. The smaller the LOB value, the greater the proportion of space for this "non-data" is used.
For example, if you have a 17-KB LOB, the 4-KB page size is the most efficient for storage. A 17-KB LOB requires five 4-KB pages for a total of 20 KB of storage space. Pages that are 8 KB, 16 KB, and 32 KB in size waste more space, because they require 24 KB, 32 KB, and 32 KB, respectively, for the LOB.
Procedure
To optimize the use of space by LOB data, use the following approaches: