Displays status information about buffers.

PROMON Buffer Cache Status display

The following shows a sample Buffer Cache Status display.

09/25/11              Status: Buffer Cache
16:21

Total buffers:                   170
Hash Table Size:                 43
Used Buffers:                    57
Empty Buffers:                   113
On lru Chain:                    168
On lru2 Chain:                   168
On apw queue:                    0
On ckp queue:                    0
Modified buffers:                170
Marked for ckp:                  0
Last checkpoint number:          0
LRU force skips:                 0
LRU2 force skips:                0

The display contains the following fields:

  • Total buffers — The total number of buffers in the buffer cache.
  • Hash Table Size — The size of the buffer hash table.
  • Used Buffers — The number of buffers currently in use.
  • Empty Buffers — The number of empty buffers.
  • On lru Chain — The number of buffers on the least recently used (LRU) chain.
  • On lru2 Chain — The number of buffers on the least recently used (LRU) chain for the Alternate Buffer Pool (-B2).
  • On apw queue — The number of buffers on the page writer queue.
  • On ckp queue — The number of buffers on the checkpoint queue.
  • Modified buffers — The number of dirty (modified) buffers.
  • Marked for ckp — The number of buffers currently marked for checkpoint.
  • Last checkpoint number — The most recent checkpoint number. As checkpoints begin, they are assigned a sequential number from the start of the session. The number is also the number of checkpoints that have occurred.
  • LRU force skips — The number of times to access a buffer before moving it to the end of the LRU chain. (A value of 0 indicates this feature is disabled.)
  • LRU2 force skips — The number of times to access a buffer in the alternate buffer pool before moving it to the end of the LRU chain. (A value of 0 indicates this feature is disabled.)