Use operating system utilities to monitor the amount of I/O activity on the disk where the BI files reside. Use the PROMON utility to monitor specific BI activity. Use the R&D option BI Log Activity. The following figure shows a sample display.
Figure 35. PROMON BI Log Activity display
Look for the following potential problems:
Busy buffer waits.
Empty buffer waits.
High number of writes per second.
High number of partial writes. A partial write occurs when the database engine must write data to the BI file before the BI buffer is full. This can happen if:
An APW attempts to write a database block whose changes are recorded in a BI buffer that has not been written. Because BI notes must be flushed before the AI note is flushed, the APW writes the data in the BI buffer before the buffer is full so it can perform the AI write.
An after-image writer (AIW) runs ahead of the BIW. Because BI notes must be flushed before the AI notes can be written, the AIW writes the BI buffer before it is full so it can perform the AI write.
The Suppress BI File Write (-Mf) parameter's timer expires before the buffer is filled.
Busy buffer waits.