title: Understanding sys.dm_exec_sessions in SQL Server
body: <p>Couple of questions on <code>dm_exec_sessions</code>. When I run the query </p>
  
  <pre><code>select * from sys.dm_exec_sessions 
  </code></pre>
  
  <p>it shows me among other columns a <code>status</code> and a <code>transaction_isolation_level</code> column. </p>
  
  <p>It is my understanding that <code>sys.dm_exec_sessions</code> returns a row per authenticated session. In my understanding several queries/transactions can be run using this session. </p>
  
  <ol>
  <li><p>What is the meaning of <code>transaction_isolation_level</code> that is returned per session? Is it the isolation level of the last transaction that was run on the database using that connection?</p></li>
  <li><p>There are some (a couple) sessions that have a status of sleeping. What does that mean? Should we be worried about this? Are these transactions from the web server that have failed to rollback?</p></li>
  </ol>