title: Using MYSQL transcations, basic questions
body: <p>I am new to db programming. 
  I read everywhere that I can use trasactions to rollback my actions if I encounter problem down the road.</p>
  
  <p>I would like to know about transactions:</p>
  
  <ol>
  <li>does a transaction "lock" the db ? </li>
  <li>If a locking happens, what happens to other users accessing the db ? is it possible that they may get an error message ? Should I programatically check for such an error and try again ?</li>
  </ol>
  
  <p>Are there things to do to make my db ready for transactions ? like setting the autocommit to off ? Is there anything else ?
  Is there a downside to using transactions ? It seems all good to me. </p>
  
  <p>Thanks in advance!</p>