title: Write Lock Schema through JDBC URL
body: <p>I've got a Java-App that is single user only. To avoid conflicts I would like to write lock the schema whenever the JDBC-connection is active. So if someone else starts the app while one instance is already running, the second will only get read-access.</p>
  <p>is there any way?</p>
  <p>If not, is there a best practice how to set and unset a flag that the app has to check on first connect?</p>
  <p>thanks</p>