The java VM does not allow heap memory exceeding 409000 bytes?!

Runtime.totalMemory() on the 6630 shows 409600. when my program reaches this limit it dies with OutOfMemory. Specification of the 6630 says, heap memory is allocated dynamically.

Why does the VM fail to increase the heap memory dynamically beyond 409600 bytes?

Did I miss some configuration detail?

Please help, Thank you