Garbage First, or G1, is a low pause, server style collector. G1's primary advantages over the Concurrent Mark-Sweep (CMS) collector include incremental compaction, better predictability and ease of use.
Although G1 is available for use in this release, note that production use of G1 is only permitted where a Java support contract has been purchased.
That loud thud you just heard? It was my jaw hitting the floor.