This is the total time required for deferred write processing. DWTOTAL displays the time in seconds, and DWTOTALM displays only the microseconds portion of the time.

Purpose

This information is collected to determine whether the deferred write processing performance is appropriate.

Evaluating the analysis results

If the deferred write delay message (KFPS02179-I factor code = A01-01) is output, take the following action:

Action to be taken

For details about the action to be taken, see 23.3.1 Tuning procedure.

This is the total time required for writing during deferred write processing. DWSUM displays the time in seconds, and DWSUMM displays only the microseconds portion of the time.

Purpose

Check whether tuning of the number of parallel write processes in deferred write processing has had any positive effect on the parallel WRITE time (DWPARA DWPARAM).

Evaluating the analysis results

Check the values of WRITE unit time (maximum) (DWMAX DWMAXM), WRITE unit time (minimum) (DWMIN DWMINM), and WRITE count (DWEXEC).

Action to be taken

Check the values of WRITE unit time (maximum) (DWMAX DWMAXM), WRITE unit time (minimum) (DWMIN DWMINM), and WRITE count (DWEXEC), and take appropriate action.

This is the time between sending of a processing request for a parallel write process for multiple deferred write processing operations, and receiving of a completion notice for the parallel WRITE process for all deferred write processing operations. DWPARA displays the time in seconds, and DWPARAM displays only the microseconds portion of the time. The following figure shows the concept of parallel WRITE time.

Figure 23-1 Concept of parallel WRITE time

If the facility for parallel writes in deferred write processing is disabled, the parallel WRITE time is 0.

Purpose

This information is collected in order to check the effects of using the facility for parallel writes in deferred write processing.

Evaluating the analysis results

If the following condition is true, use of the facility for parallel writes in deferred write processing is considered to be effective:

• Execution time (value of DWTOTAL + value of DWTOTALM) > parallel WRITE time (value of DWPARA + value of DWPARA)

For accurate checking, measure the execution time value of DWTOTAL + value of DWTOTALM) at the following times:

• Before and after the facility for parallel writes in deferred write processing is used
• Before and after the pd_dfw_awt_process operand value is changed

If the execution time is reduced, use of the facility for parallel writes in deferred write processing is considered to be effective.

Actions to be taken

If the use of the facility is effective, perform the tuning explained in 23.3.3(3) Increasing the number of parallel write processes in deferred write processing. If the use of the facility is not effective, do one of the following:

• Stop using the facility for parallel writes in deferred write processing.
• Restore the pd_dfw_awt_process operand to its original value

This is the shortest write time on a page when write operations occur on multiple pages. DWMIN displays the time in seconds, and DWMINM displays only the microseconds portion of the time.

Purpose

This information is collected in order to check how appropriate disk performance is.

Evaluating the analysis results

Evaluate performance in comparison with disk performance. If the facility for parallel writes in deferred write processing is being used, or if you change the number of parallel write processes in deferred write processing, compare the disk performance before and after use of the facility, or before and after the change.

Actions to be taken

If performance is poor compared with disk performance, use the appropriate OS function to acquire tuning information related to I/O operations, and perform tuning based on this information. If disk performance worsens when the facility for parallel writes in deferred write processing is used, or when the number of parallel write processes in deferred write processing is changed, check the parallel WRITE time. If there is no performance improvement, return the setting to the value that was in effect before use of the facility, or before the change.

One possible factor in disk performance deterioration is disk contention. Revise the disk configuration, RDAREA configuration, and table configuration as necessary to prevent I/O operations from becoming concentrated on a specific volume. For details about determining the design policies for disk configuration, RDAREA configuration, and table configuration, see the HiRDB Version 9 Installation and Design Guide.

This is the maximum write time for a page when write operations occur on multiple pages. DWMAX displays the time in seconds, and DWMAXM displays only the microseconds portion of the time.

Purpose

This information is collected in order to check how appropriate disk performance is.

Evaluating the analysis results

Evaluate performance in comparison with disk performance. If the facility for parallel writes in deferred write processing is being used, or if you change the number of parallel write processes in deferred write processing, compare the disk performance before and after use of the facility, or before and after the change.

Actions to be taken

If performance is poor compared with disk performance, use the appropriate OS function to acquire tuning information related to I/O operations, and perform tuning based on this information. If disk performance worsens when the facility for parallel writes in deferred write processing is used, or when the number of parallel write processes in deferred write processing is changed, check the parallel WRITE time. If there is no performance improvement, return the setting to the value that was in effect before use of the facility, or before the change.

One possible factor in disk performance deterioration is disk contention. Revise the disk configuration, RDAREA configuration, and table configuration as necessary to prevent I/O operations from becoming concentrated on a specific volume. For details about determining the design policies for disk configuration, RDAREA configuration, and table configuration, see the HiRDB Version 9 Installation and Design Guide.

This is the average write time when write operations occur on multiple pages. DWAVG displays the time in seconds, and DWAVGM displays only the microseconds portion of the time.

Purpose

This information is collected in order to check the validity of disk performance.

Evaluating the analysis results

Evaluate performance in comparison with disk performance. If the facility for parallel writes in deferred write processing is being used, or if you change the number of parallel write processes in deferred write processing, compare disk performance before and after use of the facility, or before and after the change.

Actions to be taken

If performance is poor compared with disk performance, use the appropriate OS function to acquire tuning information related to I/O operations, and perform tuning based on this information. If disk performance worsens when the facility for parallel writes in deferred write processing is used, or when the number of parallel write processes in deferred write processing is changed, check the parallel WRITE time. If there is no performance improvement, return the setting to the value that was in effect before use of the facility, or before the change.

One possible factor in disk performance deterioration is disk contention. Revise the disk configuration, RDAREA configuration, and table configuration as necessary to prevent I/O operations from becoming concentrated on a specific volume. For details about determining the design policies for the disk configuration, RDAREA configuration, and table configuration, see the HiRDB Version 9 Installation and Design Guide.

This is the write count for each operational cause (CAUSE).

Purpose

This information is collected to determine whether deferred write processing is delayed for the following reason:

• The number of update buffers that can be processed is exceeded within the synchronization point collection interval.

Evaluating the analysis results

If the operational cause (CAUSE) is S (synchronization point), check to see if the WRITE count (DWEXEC) is equal to or less than the value obtained from the formula below. If the WRITE count is greater than the value, take appropriate action, as described below.

{synchronization point collection interval average WRITE unit time (DWAVG, DWAVGN)} 0.1

Obtain the synchronization point collection interval from the difference between the output times of the following messages:

• KFPS02183-I (message displayed when synchronization point processing is completed)
• KFPS02179-I (message displayed when synchronization point processing is skipped)

Actions to be taken

Tune by reducing the number of update buffers during synchronization point processing. For details about the tuning method, see 23.3.3(1) Reducing the deferred write trigger interval and 23.3.3(2) Increasing the update page output rate during deferred write trigger.

If the tuning does not help, specify the pd_dfw_syncpoint_skip_limit operand and limit the number of update buffers. In this case, however, if the skip count for the synchronization point processing reaches the maximum value, the update buffer is output at an extension of the update transaction, thereby adversely affecting the update transaction performance.