code: public static PersistenceManager openOrCreateDB(String dbName) { 
      	DBTracer.logCall(ZooJdoHelper.class, dbName); 
      	if (!dbExists(dbName)) {
      		createDb(dbName);
      	}
      	return openDB(dbName);
      }
docs: Open a database.
  Create the database file if it doesn't exist.
  
  This is short for: <br>
  <code>
  ZooJdoProperties props = new ZooJdoProperties(dbName);  <br>
  PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory(props);  <br>
  PersistenceManager pm = pmf.getPersistenceManager();  <br>
  if (!dbExists(dbName)) { <br>
  createDb(dbName); <br>
  } <br>
  </code>
  
  @param dbName Name of the database to connect to.
  @return A new PersistenceManager