The Buffer Manager object provides counters to monitor how SQL Server uses:

* Memory to store data pages, internal data structures, and the procedure cache. * Counters to monitor the physical I/O as SQL Server reads and writes database pages.

Monitoring the memory and the counters used by SQL Server helps you determine:

* If bottlenecks exist from inadequate physical memory. If it cannot store frequently accessed data in cache, SQL Server must retrieve the data from disk. * If query performance can be improved by adding more memory, or by making more memory available to the data cache or SQL Server internal structures. * How often SQL Server needs to read data from disk. Compared with other operations, such as memory access, physical I/O consumes a lot of time. Minimizing physical I/O can improve query performance.

You can also monitor Address Windowing Extensions (AWE) activity in SQL Server with the AWE counters. For example, you can make sure that SQL Server has enough memory allocated for AWE to run properly.