Adaptive Server uses LRU strategy for:
Statements that modify data on pages
Pages that are needed more than once by a single query
OAM pages
Most index pages
Any query where LRU strategy is specified
LRU replacement strategy reads the data pages sequentially into the cache, replacing a “least recently used” buffer. The buffer is placed on the MRU end of the data buffer chain. It moves toward the LRU end as more pages are read into the cache.
Figure 2-2: LRU strategy takes a clean page from the LRU end of the cache