What is the buffer pool?

The buffer pool is a major SQL Server memory area used to cache database pages and reduce repeated physical disk reads.

When a query needs a data or index page, SQL Server checks whether it is already in memory. If not, the page is read from storage into the buffer pool. Modified pages become dirty pages and can later be written to disk.

Good performance depends on the interaction of memory, storage, query patterns, indexes, and workload—not simply on maximizing cache hit percentages.