title: Postgresql 9.3: changing the value of SYSTEM parameters like log_lock_waits
body: <p>I am getting following error on ALTER SYSTEM query</p>
  
  <pre><code>db_live=# ALTER SYSTEM SET log_lock_waits To on;
  ERROR:  syntax error at or near "SYSTEM"
  LINE 1: ALTER SYSTEM SET log_lock_waits To on;
  </code></pre>
  
  <p>I also tried changing the value in postgresql.conf and restarting the server, but it is not being reflected in SYSTEM variables when I run 'SHOW ALL'. It is happening for all other SYSTEM parameters too.</p>