Does CA have recommendations on how to tell when a CICS region should go from a Single Socket Listener to one Multi-socket listener?
CA GEN Release 8.5
Typically, customers do not move from one Listener to the other because of capacity but rather because of slow response/hang conditions across their clients. This occurs if a transaction being processed by the Single Sockets Listener encounters an error and it suspends/locks the listener for duration of the GIVTIME time, which is the time it takes for the Givesocket to fail. Other transactions wait in a backlog for the Listener to process them.
If your users report slow response or unusual waits, you should look at changing to the Multi Socket Listener. But, if they do not see any problems, they can wait and do it when they feel is a good time in their schedule.
The Multi Socket Listener puts out a message when it terminates that indicates the high water mark for the number of sockets used by the listener for this execution:
TISRVMSL TIML TASK=00000038 08/26/2016 15:52:40 LISTENER ENDED - NORMAL TERMINATION, TIML
TISRVMSL TIML TASK=00000038 08/26/2016 15:52:40 MOST SOCKETS USED: 00001
EZY1278I 08/26/16 15:52:40 EZACIC03 DETACH SUCCESSFUL TCB ADDRESS=007B3AA0 TRAN=TIML TASK=00000038
The Single Socket Listener does not. Since the Single Socket Listener single streams the requests, it does not use more than 3 sockets at any time.