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Refers to average percentage of SQL Server processor usage on the computer hosting the SQL Server instance.
SQL Memory Usage/Allocated
Refers to amount of memory in use by the monitored SQL Server instance.
SQL Disk I/O
Refers to the number of physical reads and physical writes made by the SQL Server instance between refreshes. If you see a high percentage of physical reads , you can improve performance by allocating more memory to the SQL data cache.
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