I/O cache; Page cache
Cost constraints (dollars per gigabyte) prohibit in-memory databases in most cases, but processors can access and manipulate data only while it is in memory. The in-memory buffer pool holds database pages currently in use and retains those deemed likely to be used again soon.
The buffer pool and the buffer management component within the storage layer of a database management system provide fast access and fast recall of on-disk pages using in-memory images of those pages. In addition to the size of individual pages and of the entire buffer pool, key issues are (i) page replacement in response to buffer faults, and (ii) page retention and update in aid of database recovery.
A database buffer pool differs from virtual memory as it contributes to correctness and efficiency of query and update processing, e.g., by pinning pages while in use and by ensuring a write sequence that guarantees the ability to recover. In some systems, the buffer pool...
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