I assume that by "J2EE 1.6" you mean "JEE 6", the most-recent-but-one version of the JEE standard (it hasn't been called J2EE since 2006).
The container can do very little to handle scalability, besides handling incoming requests as fast as possible. Some configurations play a role in this (max. JVM memory, size of
thread pool for incoming connections, size of DB connection pool if applicable etc.), but those will vary according to the specifics of your app - you'd need to
test and decide what good values are. While some containers provide load balancing features, that is outside the scope of JEE.