The prefetch ratio for a buffer pool, shown as a percentage. This value is the ratio of asynchronous reads to logical read requests. It is a measure of how efficiently pages are being prefetched into the buffer pool from disk so that they are available when read requests are made. Prefetching allows applications to access pages more quickly than when the pages must be read from disk. A higher percentage means a lower frequency of disk I/O and less I/O wait time.