Start PROMON for the database you intend to establish as the source database by using the following command:

promon db-name

Once PROMON is running, do the following:

  1. Type R&D in the Enter your selection field, and press ENTER.
  2. Type 5 to select Adjust Monitor Options, and press ENTER.
  3. Type 3 to select Monitor sampling interval, and press ENTER.
  4. Type 3600 in the Enter sample interval <1 to 3600> field, and press ENTER twice.
  5. Type 2 to select Activity Displays, and press ENTER.
  6. Type 6 to select AI Log, and press ENTER.

The Activity: AI Log appears, as shown:

01/23/12        Activity: AI Log
14:29:40        01/23/12 14:26 to 01/23/12 14:29 (3 min 9 sec)

                              Total         Per Min      Per Sec	     Per Tx
    
Total AI writes                   2               1         0.01		        1.00
AIW AI writes                     0               0         0.00		        0.00
Records written                  68              22         0.36		       34.00
Bytes written                  7379            2343        39.04		     3689.50
Busy buffer waits                 0               0         0.00		         0.00
Buffer not avail                  0               0         0.00		         0.00
Partial writes                    1               0         0.01		         0.50
Log force waits                   0               0         0.00		         0.00
 Enter <return>, A, L, R, S, U, Z, P, T, or X (? for help):

Notice the elapsed time (shown here in bold) on the second line of the sample log.

Example

To gather a sample for 60 minutes:

  1. Type S and press ENTER. The message "Sampling for 3600 . . . " appears. When the 60 minutes have elapsed, the numbers shown on the rest of the screen reflect running totals for that elapsed time.
  2. Record the number from the Total AI writes row in the Total column. This is the total number of after-image blocks written in one hour. You can repeat this process to gather additional samples.

    Calculating a realistic average number of blocks written in one hour requires several samples. The more samples you gather, the more accurate the average is.

  3. Divide the average number of blocks generated in one hour by after-image block size. The after-image block size can be found from the main menu of R&D by selecting option 1 (Status Displays) and then option 10 (AI Log). The after-image block size is the second-to-last entry.
  4. Take this number and divide it by 1024 to arrive at the block size (8192 / 1024 = 8).
  5. Multiply the value from the activity menu by the value calculated. The result is the number of 1K after-image blocks written during a typical hour period.