The OS Disk Time (Percent) alert provides the percentage of elapsed time that all disks are busy servicing read and write requests on the SQL Server computer.

Reduce OS processor time

If this value regularly exceeds 75%, you should take action such as:

• Reduce the number of SQL re-compilations since they are CPU intensive. There are many reasons that an object such as a stored procedure is recompiled and you can remove most of these reasons by careful coding. See the SQL Re-compilations counter for ways to dramatically reduce recompiles.
• Make sure that all T-SQL statements (whether in a stored procedure, trigger, or ad hoc statement) that reference objects fully qualify the object referenced. For example: SELECT * FROM Northwind.dbo Employees is a fully-qualified object reference whereas SELECT * FROM Employees is a poorly-qualified object. You can reuse the execution plans of fully-qualified objects "as is," whereas plans where you either cannot reuse the not fully-qualified objects or, if they are reused, then they are subject to a highly restrictive COMPILE lock while SQL Server determines if all of the objects referenced in the T-SQL code have the same owners as the execution plan currently in cache. Both of these situations consume a significant amount of CPU time.
• Stop unnecessary programs (such as the Print Spooler or activities such as the database server acting as either a BDC or PDC) from running.