Tuning IMS
To tune IMS for better performance, you can generate IMS performance advisor reports that provide recommendations and changes to the system. For more information about generating these reports, see Generating batch performance advisor reports.
IMS performance advisor reports
You can generate the following types of advisor reports:
Report 1—Identify which transactions should be assigned as wait-for-input (WFI)
You can use this report to improve IMS transaction response time. The report recommends which transactions you should assign to WFI or a PWFI region, and how many WFI or PWFI regions are required for each reassigned transaction.
This method reduces the need for an experienced systems programmer, the time to analyze the data, and guesswork. This process provides accurate suggestions for making changes to the system with precise metrics.
By using this report, you can perform the following actions:
- Reduce transaction queue time because WFI and P-WFI do not go through complicated scheduled logic. The program does not need to restart and is ready to take on a new transaction
- Reduce CPU consumption, especially for transactions accessing Db2 resources.
- Reduce storage allocation for IMS regions due to program preload.
- Reduce I/O loading the application programs because WFI transactions do not terminate.
- Improve response time as a result of the time reduction.
Report 2—Identify high volume transactions that qualify for a new class
You can use this report to identify transactions that have high volume, but not high enough to warrant a separate Message Processing Region (MPR). You can then group these high-volume transactions together and assign them into a new class to run in a P-WFI environment. It is not necessary to add new MPRs for the new class, and you can instead reuse the existing MPRs for the original class.
By doing this, the transactions are much more likely to be scheduled without the scheduling overhead due to P-WFI, and with less interference from other low-volume transactions. Therefore, you can reduce the CPU that IMS and transactions response time use.
Report 3—Identify how many Message Processing Regions (MPRs) you should have in your IMS environment
You can use this report to tune the number of IMS MPRs that you are using. The report recommends how you should allocate the number for IMS MPRs for a particular timeframe. By using IMS log data sets, this process analyzes each region by calculating its region occupancy, class assignment, transaction elapsed time, and the number of MPRs running the class. It then provides recommendations to set up MPRs based on your input.
This process reduces the need for an experienced systems programmer, the time to analyze the data, and guesswork. This process provides accurate suggestions for making changes to the system with precise metrics.
By using this report, you can perform the following actions:
- Reduce CPU consumption due to less system overhead
- Reduce system paging due to correct MPR allocation
- Reduce virtual storage allocation such as CSA and ECSA