title: what is the use of the pool option in database.yml
body: <p>Most widely used options in database.yml are of following :</p>
  
  <pre><code>adapter
  encoding
  database
  pool
  username
  password
  socket
  host
  port
  timeout
  </code></pre>
  
  <p>I know the use of the most of the above but pool.
  So i want to know what is the use of the pool option in database.yml or there is any other parameter which we need to set for the application having very heavy traffic.</p>