On a CA IDMS CV, is there a way to calculate CPU utilization based on statistics for physical reads?

Products

• IDMS
• IDMS - Database

Issue/Introduction

An IDMS CV can be tuned many ways to maximize performance. One such option is to tune buffers, which may reduce physical reads. Clients may want to calculate the impact of such tuning changes on their CPU utilization. 

Environment

Release : 18.5 & 19.0

Component : CA IDMS/DB

Resolution

     In terms of determining the CPU impact of a tuning change, such as a reduced number of physical reads, there is no way to compute that. That is because there is no direct ratio or even estimate of how those two factors interrelate; it depends on too many factors such as the specific hardware involved, operating system, etc.  

    If there is a need to determine the change in CPU based on tuning changes, a baseline is necessary. The same is true if there is a need to determine the impact of tuning changes on throughput and response time. That process of getting a baseline and doing before and after comparisons would be most effective if the following steps re implemented:

1- put together an isolated test on a CV for which I have total control;

2- run a series of transactions;

3- note the number of Phys Reads done (or whatever statistic is being tracked / targeted by the tuning);

4- shutdown CV and look at CPU statistics; 

5- then bring that CV back up with larger buffers;

6- run the exact same series of transactions;

7- note how many fewer physical reads were done (or whatever statistic is being tracked, as noted above), and;

8- shut down the CV and compare CPU time for that cycle of CV to the first test. 

This is the only guaranteed way to get accurate information about how tuning changes impact the CPU utilization.