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Planning for a Db2 for z/OS Upgrade: Application Testing

October 31, 2017

I recently received this question about upgrading to Db2 12:

Our shop will be upgrading to DB2 V12 z/OS and typically we do extensive testing with any new release in both CM and NFM. If we will not be using any of the new functionalities in our applications, and we test in CM (function level 100), do we really need to test again in NFM (function level 500)?

This got me to thinking about resources devoted to planning for Db2 for z/OS upgrades. This Julian Stuhler post nicely lays out the tasks that should be in your upgrade plans.

As for application regression testing, customers are typically concerned about performance regression for critical transactions. For instance, if a critical transaction currently completes in less than a second, you don't want that transaction taking more than 1 second post-upgrade. Julian talks about establishing a performance baseline to deal with these sorts of issues.

The other area of application regression testing is verifying that the application runs without errors and the data is what’s expected. When I say run without error, the application could be using SQL features that have changed in functionality between releases. As part of the planning as stated in Julian’s list, “application incompatibilities” are fully documented in the installation and migration documentation. Another good source is this IBM Redbook. In particular, check out the section titled, “How to find applications that use incompatible SQL statements?”

As for the original question, it has a simple answer: no. You don't need to do the same full regression testing when activating functional level 500 (previously known as NFM mode) that you did when activating function level 100 (previously known as CM mode).

While in Db2 12 function level 100, all the application packages and plans should be rebound with application compatibility set to the minimum of V10R1. This REBIND process will rebuild the Db2 object structures and pass the SQL through the new Db2 optimizer code, which could generate a new and improved access path. It's this newly created Db2 package structure that will be tested during the regression testing. Now when you activate function level 500, the applications will continue to run using the same access path. No new testing is needed.

Posted October 31, 2017 | Permalink

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