Displays information about BI log activity.

PROMON BI Log Activity display

The following shows a sample BI Log Activity display.

09/28/06        Activity: BI Log
15:22:38        09/28/06 10:50 to 09/28/06 15:22 (4 hrs 32 min)

                              Total        Per Min    Per Sec        Per Tx
Total BI writes                1517              6       0.09        758.50
BIW BI writes                   956              4       0.06        478.00
Records written              116270            428       7.13      58135.00
Bytes written               9996664          36768     612.80    4998332.00
Total BI Reads                  386              1       0.02        193.00
Records read                  26923             99       1.65      13461.50
Bytes read                  2330572           8572     142.87    1165286.00
Clusters closed                  19              0       0.00          9.50
Busy buffer waits               588              2       0.04        294.00
Empty buffer waits               29              0       0.00         14.50
Log force waits                   0              0       0.00          0.00
Log force writes                  0              0       0.00          0.00
Partial writes                  222              1       0.01        111.00
Input buffer hits               388              1       0.02        194.00
Output buffer hits              135              0       0.01         67.50
Mod buffer hits                 431              2       0.03        215.50
BO buffer hits                53169            196       3.26      26584.50

The display lists the following types of BI operations:

  • Total BI writes — The number of writes to the BI file.
  • BIW BI writes — The number of writes to the BI file performed by the before-image writer (BIW). For good performance, this number should be high in relation to the total number of BI writes.
  • Records written — The number of BI records (notes) written to the BI file.
  • Bytes written — The amount of data written to the BI file, in bytes.
  • Total BI Reads — The number of BI blocks read from the BI file (to undo transactions).
  • Records read — The number of BI records (notes) read from the BI file.
  • Bytes read — The amount of data read from the BI file, in bytes.
  • Clusters closed — The number of BI clusters filled and closed in preparation for reuse.
  • Busy buffer waits — The number of times a process had to wait for someone else to finish before being able to write to a BI file.
  • Empty buffer waits — The number of times a process had to wait because all buffers were full.
  • Log force waits — The number of waiting-for-commit records to be written to disk.
  • Log force writes — The number of waiting-for-commit records written to disk.
  • Partial Writes — The number of writes to the BI file made before the BI buffer is full. This might happen if:
    • The Delayed BI File Write (-Mf) parameter timer expired before the buffer was filled.
    • An APW attempts to write a 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 AIW writes the data in the BI buffer before the buffer is full so it can do the AI write.
    • An AIW ran 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 do the AI write.
  • Input buffer hits — The number of times a note needed to back out a transaction was found in the Input BI buffer. The Input BI buffer is a shared buffer that contains the BI block needed for a transaction blackout if the note could not be found in the Output BI buffer or the Mod BI buffers. The Input BI buffer is read back into memory from the BI log.
  • Output buffer hits — The number of times a note needed to back out a transaction was found in the Output BI buffer. The Output BI buffer is a shared buffer that contains the BI notes currently being written to disk.
  • Mod buffer hits — The number of times a note needed to back out a transaction was found in the Mod BI buffers. The Mod BI buffers are shared buffers that are being updated with notes for currently executing transactions. The Mod BI buffers have not been written to disk.
  • BO buffer hits — The number of times a note needed to back out a transaction was found in a private BO (Back out) buffer. Back out buffers are private buffers allocated, one per user, after transaction blackout processing twice locates the required note in the Input BI buffer. BO buffers reduce contention for the Input BI buffer when more than one user is simultaneously backing out transactions.