IDMS performance degrades and ILTE abends after change to front-end/back-end

Products

• IDMS
• IDMS - Database
• IDMS - ADS

Issue/Introduction

  We had a single production CV where all users signed on and all databases where accessed.
  Made the change to multiple "DC-only" front-end CVs and one back-end CV where all application database access was done.
   The front-end CVs connected to the back-end by means of SVC type NODE definitions.
    Once a full load of users were engaged we experienced many "bottlenecks" causing poor response time and also a large number of ILTE abends on back-end CV.

Environment

Release: IDADSO00100-18.5-ADS-for CA-IDMS
Component:

Resolution

  The SVC type NODE connections to back-end require the use of an ERE (External Request Element) on the back-end.  
   Prior to the switch to the front-end/back-end configuration there were only a small number of external programs (ERUS) accessing the CV so the sysgen defined only 10 EREs (MAXIMUM ERUS IS 10 on the Sysgen SYSTEM statement).
   This was the cause of the bottlenecks.
    Changing MAX ERUS to 225 on the back-end CV resolved the bottlenecks.
  
     The ILTE abends on the backend were caused by the fact that RESOURCE TIMEOUT was the same on both front-end and back-end.
     We changed front-end CVs to have RESOURCE TIMEOUT INTERVAL 240  and the back-end CVs  RESOURCE TIMEOUT INTERVAL 300.
     This stopped the ILTE abends.