title: how to check sql_trace in oracle database?
body: <p>I am newbie in Oracle database.
  I want to ask how to check sql_trace of oracle system? 
  I made mistake run these command
  <code>ALTER SYSTEM SET sql_trace = true</code>
  without checking the status first. 
  I already googling but can not find how to check the <code>sql_trace</code> status true or not. 
  I have two similar database, so I want to check status on the other database and set it same status in another database.</p>