Access Methods – Full scans/sec: higher numbers (> 1 or 2) may mean you are not using indexes and resorting to table scans instead.
Buffer Manager – Buffer Cache hit ratio: This is the percentage of requests serviced by data cache. When cache is properly used, this should be over 90%. The counter can be improved by adding more RAM.
Memory Manager – Target Server Memory (KB): indicates how much memory SQL Server “wants”. If this is the same as the SQL Server: Memory Manager — Total Server Memory (KB) counter, then you know SQL Server has all the memory it needs.
Memory Manager — Total Server Memory (KB): much memory SQL Server is actually using. If this is the same as SQL Server: Memory Manager — Target Server Memory (KB), then SQL Server has all the memory it wants. If smaller, then SQL Server could benefit from more memory.
Locks – Average Wait Time: This counter shows the average time needed to acquire a lock. This value needs to be as low as possible. If unusually high, you may need to look for processes blocking other processes. You may also need to examine your users’ T-SQL statements, and check for any other I/O bottlenecks.