End of MLRU cleaning

You can also specify the point at which MLRU cleaning can end.

The lru_min_dirty value in the BUFFERPOOL configuration parameter specifies the acceptable percentage of buffers in an MLRU queue. For example, if lru_min_dirty is set to 50.00, page cleaning is not required when 50 percent of the buffers in an LRU queue are modified. In practice, page cleaning can continue beyond this point, as directed by the page-cleaner threads.

The following example shows how the value of lru_min_dirty is applied to the LRU queue to specify the acceptable percent of buffers in an MLRU queue and the point at which page cleaning ends.
Buffers specified as 8000
lrus specified as 8
lru_min_dirty specified as 50 percent

The acceptable number of buffers in the MLRU queue and 
   the point at which page cleaning can end is equal 
   to lru_min_dirty. 

Buffers per LRU queue = (8000/8) = 1000

Acceptable number of buffers in MLRU queue and the point 
   at which page cleaning can end: 1000 x .50 = 500

You can use decimals for the lru_max_dirty and the lru_min_dirty values. For example, if you set lru_max_dirty to 1.0333 and lru_min_dirty to 1.0, this triggers the LRU to write at 3,100 dirty buffers and to stop at 3,000 dirty buffers.

For more information about how the database server flushes the buffer pool, see Flush data to disk.

Copyright© 2018 HCL Technologies Limited