title: How to check performance of a SQL Server database?
body: <p>I restarted my dedicated server this morning. as a result my SQL Server was very responsive. I could query 1.500.000 records table, results returns within couple secs.</p>
  
  <p>after a while I see my CPU started growing, and it's not so fast anymore 30-50 secs for the same queries.</p>
  
  <p>I checked sp_who2, no blocking transactions. I rebuilt the index. No changes still slow</p>
  
  <p>What is the best way to troubleshoot this kind of behaviour? How to improve performance?</p>
  
  <p>Here is my task manager</p>
  
  <p><img src="https://i.stack.imgur.com/XG0B7.png" alt="enter image description here"></p>