explain what the irule is exactly doing

Thank you Stanislas,

My next question is which parameters in F5 (either from the command line or GUI affect this persistance record timeout.

In our case we have 2 x tomcat servers and only one is the one "in persistance" no load balancing. When the F5 detects that the tomcat is down (port 9090 for us), the F5 starts sending packets to the other tomcat, which was in stand-by mode. The fact is that there is a period of time (30-40 seconds) that the F5 is sending packets to BOTH tomcats and thus there is a mess. The fact is that the F5 does not seem to make a "sudden death" situation where if A is active, I send packets only to A and when there is a switch over then packets are sent only to B. There is a gray period on this. I do not know by how much the above irule is helping.

Awaiting for any suggestions. Many thanks