Configuration Parameters That Affect Sbspace I/O

The following configuration parameters affect the I/O performance of sbspaces:

• SBSPACENAME
• BUFFERPOOL
• LOGBUFF

SBSPACENAME

The SBSPACENAME configuration parameter indicates the default sbspace name if you do not specify the sbspace name when you define a column of data type CLOB or BLOB. To reduce disk contention and provide better load balancing, place the default sbspace on a separate disk from the table data.

BUFFERPOOL

The size of your memory buffer pool affects I/O operations for smart large objects because the buffer pool is the default area of shared memory for these objects. If your applications frequently access smart large objects, it is advantageous to have these objects in the buffer pool. Smart large objects only use the default page size buffer pool. For information on estimating the amount to increase your buffer pool for smart large objects, see Smart Large Objects and Buffers.

By default, the database server reads smart large objects into the buffers in the resident portion of shared memory. For more information on using lightweight I/O buffers, see Lightweight I/O for Smart Large Objects.

LOGBUFF

The LOGBUFF parameter affects logging I/O activity because it specifies the size of the logical-log buffers that are in shared memory. The size of these buffers determines how quickly they fill and therefore how often they need to be flushed to disk.

If you log smart-large-object user data, increase the size of your logical-log buffer to prevent frequent flushing to these log files on disk.

The user-data portion of smart large objects that are logged does not pass through the physical log, so you do not need to adjust the PHYSBUF parameter for smart large objects.