There are two LRU management methods:
With this method, reference buffers and update buffers are managed by independent LRUs.
If a shortage occurs in the global buffers, the least recently accessed reference buffer from among the global buffers is removed from the memory.
In the following case, it is preferable for the reference buffer and the update buffer to be managed in separate LRUs:
If a large amount of update processing occurs, the reference buffer hit rate drops, slowing down retrieval processing.
SEPARATE is specified in pd_dbbuff_lru_option in the system common definition.
With this method, the global buffers are managed collectively by one LRU.
If a shortage occurs in the global buffers, the least recently accessed buffer from among the global buffers is removed from the memory.
It is beneficial to employ batch LRU management of global buffers in the following case:
MIX is specified in pd_dbbuff_lru_option in the system common definition.
The updated output page rate for deferred write trigger is specified in the -w option of the pdbuffer operand in the system common definition.