Summary Info:

Logical Reads : Reading Data pages from Cache

Physical Reads : Reading Data pages from Hard Disk

Buffer Cach Hit Ratio :(logical reads – physical reads)/logical read * 100%

Details Info:

Logical Reads:

Logical read indicates total number of data pages needed to be accessed from data cache to process query. It is very possible that logical read will access same data pages many times, so count of logical read value may be higher than actual number of pages in a table. Usually the best way to reduce logical read is to apply correct index or to rewrite the query.

Physical Reads

Physical read indicates total number of data pages that are read from disk. In case no data in data cache, the physical read will be equal to number of logical read. And usually it happens for first query request. And for subsequent same query request the number will be substantially decreased because the data pages have been in data cache.

Buffer Cash Hit Ratio

Buffer hit ratio will be calculated based on these two kinds of read as the following formula: (logical reads – physical reads)/logical read * 100%. The high buffer hit ratio (if possible to near 100%) indicates good database performance on SQL Server level. So use information from physical read and buffer hit ratio to measure performance in server level and logical read to measure individual query level

Thanks,

Dinesh Babu Verma