Displays information about checkpoints.

PROMON Checkpoints display

The following shows a sample Checkpoints display.
♀07/02/24        Checkpoints
10:06:28

Ckpt                                     ------------- Database Writes --------------  --------- Performance Timings --------
 No. Time        Len   Freq     Dirty    CPT Q     Scan    APW Q  DB Writes BI Writes  Duration  Sync Time  DB Write  BI Write      NumChkpt  BI Cluster  Waits  WaitTime ClFil%  FuzzTm

 567 10:14:52      4      4     23290    23282        0        0          0         0      1.62       1.56      0.02      0.05        23282           3      0 	0.00		100     4
 566 10:14:47      5      5     23734    23726        0        0          1        18      1.58       1.39      0.02      0.15        23726           2      0 	0.00	    100     5
 565 10:14:39      7      8     23539    23533        0        0          0        18      1.52       1.39      0.02      0.09        23533           1      0 	0.00	    100     7
 564 10:14:31      8      8     23808    23801        0        0          0        11      1.49       1.41      0.04      0.03        23802           8      1 	0.02	    100     8
 563 10:14:27      4      4     23411    23033        0        0        372         0      1.42       1.34      0.03      0.05        23033           7      0 	0.00	    100     4
 562 10:14:22      5      5     23761    23752        0        0          0        17      1.33       1.27      0.03      0.03        23752           6      0 	0.00	    100     5
 561 10:14:17      5      5     23379    23369        0        0          0         0      1.41       1.33      0.02      0.06        23370           5      1 	0.00	    100     5
 560 10:14:13      4      4     23399    23389        0        0          2         0      1.35       1.30      0.01      0.03        23389           4      0 	0.00	    100     4
 559 10:14:08      5      5     23576    23571        0        0          0         0      1.37       1.30      0.02      0.04        23571           0      0 	0.00	    100     5
 558 10:14:03      5      5     23668    23662        0        0          0        11      1.34       1.28      0.02      0.04        23662           3      0 	0.00	    100     5
 557 10:13:59      4      4     23457    23451        0        0          0         0      1.31       1.25      0.03      0.03        23451           2      0 	0.00	    100     4
 556 10:13:54      5      5     23947    23940        0        0          0        18      1.51       1.42      0.03      0.07        23940           1      1 	0.02	    100     5

This display shows the following information:

  • Ckpt. No. — The sequential number assigned to the checkpoint
  • Time — The time the checkpoint began
  • Len — The length of time required to complete the checkpoint. The checkpoint is not considered completed until all dirty buffers on the checkpoint queue have been written out. This is either done over time by the APWs between checkpoints or is forced at the next checkpoint (DB Writes).
  • Freq — The length of time between checkpoint starts
  • Dirty — The number of modified buffers scheduled to be written
  • Database Writes
    • CPT Q — The number of buffers written from the checkpoint queue by the APWs
    • Scan — The number of buffers written by the APWs during the scan cycle
    • APW Q — The number of buffers written by the APW queue and replaced on the least recently used (LRU) chain by APWs
    • DB Writes — The total number of database buffers written all at once at the end of the checkpoint
    • Bi Writes — The total number of BI buffers written from the BI buffer pool all at once at the end of the checkpoint
  • Performance Timings
    • Duration — The time to do the housekeeping of the checkpoint. This includes the time to write the active recovery log buffers to disk, write any outstanding dirty buffers marked at the previous checkpoint, scan the database buffer pools for dirty buffers marking them as needing to be written to disk prior to the start of the next check point (putting them on the checkpoint queue) and to perform the file system synchronization (Sync Time).
    • Sync Time — The time to perform the file system synchronization of the checkpoint (fdatasync() on UNIX, FlushFileBuffers() in Windows)
    • DB Write — The time in seconds to scan and write the buffers from the database buffer pool
    • Bi Write — The time in seconds to write the buffers from the -bibufs buffer pool
    • NumChkpt — The number of buffers checkpointed (written from the database buffer pool)
    • Waits — The total number of dirty buffers in the writing state that are being waited for at a checkpoint
    • WaitTime — The total wait time in seconds at the current checkpoint for dirty buffers to transition from the changed or writing state