Gen Single and Multi Sockets Server Listener Health Check

Products

• Gen
• Gen - Run Time Distributed

Issue/Introduction

Are there recommendations on how to tell when a CICS region should go from a Gen CICS Single Sockets Server Listener to a Gen CICS Multi Sockets Server Listener? 

Environment

Gen TCP/IP Direct Connect for CICS

Resolution

Typically, it is not required to move from one Listener to the other because of capacity but rather because of slow response/hang conditions across the Gen clients.
This occurs if a transaction being processed by the Single Sockets Server 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 users report slow response or unusual waits, look at changing to the Multi Sockets Server Listener.

Additional Information

The Multi Sockets Server 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 Sockets Listener does not and because it single streams the requests, it does not use more than 3 sockets at any time. 


NOTE:
The Single Socket Listener is deprecated: Gen™ 8.6 > Release Notes > Gen 8.6 GA Complete (8.6.2) > Gen Release 8.6
The CICS Sockets Server Listener
The CICS Sockets Server Listener (program TISRVLIS) was deprecated in Gen Release 8.5. It is still
supported in Gen 8.6, but is not enhanced with any new functionality. The CICS Multi Sockets Server
Listener (program TISRVMSL) is the replacement product.