In my production environment, I recently saw that no one could log on as the listner state was blocked.
Service "prd002l" has 1 instance(s).
Instance "prd002l", status READY, has 1 handler(s) for this service...
"DEDICATED" established:12730 refused:0 state:blocked
This is IBM-AIX 5.3 envoronment. CPU = 2 Memory = 16GB