When to implement IDMS Multitasking

Products

• IDMS
• IDMS - Database
• IDMS - ADS

Issue/Introduction

Sites may want to know how to determine whether a particular IDMS CV is suitable to change to MultiTasking (MT). They may wonder whether there is a report that can be run to indicate whether or not this is a good candidate. 

CA IDMS is a multithreaded system that supports multiple diverse units of work called tasks. In the past, these tasks shared one operating system subtask. With multitasking support, several CA IDMS tasks can execute concurrently and each task uses a different predefined operating system subtask.

Environment

IDMS supports MultiTasking in any Z/OS environment. 

Resolution

      IDMS does not have any predictive reports that would show whether or not a CV is a good candidate for MultiTasking,. Most folks considering this feature use the PMARPT02 and DCMT commands to test whether or not MultiTasking is improving response time for their users by running them before and after implementing it, and comparing results..  
 
      The main reason sites implement Multitasking (MT) on their IDMS CVs is in an effort to improve response time for their applications, by reducing wait time. To implement MT, however, will require slightly more CPU than running a CV without Multitasking. For most sites this increase in CPU is neglibible, but it could have an impact if your shop is already not getting enough CPU allocations from Z/OS to the CV. Therefore, one thing to review before activation of MT, is to check the effectiveness of MVS CPU allocated by z/OS to your IDMS region. It is useless or even painful to allocate extra TCB's to your IDMS region if z/OS doesn't allocate enough CPU to your IDMS region. MT uses MPMODE locking which will consume a small amount of extra CPU. If you are getting ample CPU allocated to IDMS, & if your applications are running too slowly to satisfy your end users, then it could be worth your while to try implementing MT to see if it helps. After MT activation, watch your TCB's usage with DCMT DIS MPMODE and DCMT DIS SUBTASK EFFECTIVENESS . 
 
     You can find a general discussion about Multitasking at Multitasking Support: 
This includes an explanation of how multi=tasking works, as well as ways to monitor the impact Multitasking is having on your CV. PMARPT02, the Task Summary Report, which you mentioned, is a great way to measure changes in overall response time before and after implementing multitasking. This will let you know whether or not the Multitasking has had the desired effect. 
 
     There is also a community discussion about MultiTasking that you may find helpful, which can be found here: 
https://communities.ca.com/thread/241769906-is-anyone-using-idms-multi-tasking