What do you mean by "sleep mode"
There is no such thing.
What is the limiting factor you are seeing?
Too many network connections? - the connections are put
in a backlog
CPU maxing out? - this would indicate your selector is the problem
Memory is full? jboss moves messages to disk to free memory
Waiting for database connections from the pool?
if you are using the default hsqldb setting (not recommended)
there is a maximum of 20 db connections - everybody else waits.
If the database is slow, everybody else waits.
Figure out what your limiting factor is, then come back to