IBM® launched the consolidated service test (CST) effort in November 2000 and redefined the Recommended Service Upgrade (RSU) for the OS/390® and z/OS® platforms in November 2001. The objective was to provide a consolidated, tested, and recommended set of service for z/OS and key subsystems on a quarterly basis with published results. This means that you can obtain and install service for z/OS and key subsystems from one recommended service package, so that you have a tested level of service for all these products.

The CST team tests in a customer-like production Parallel Sysplex® environment in an IBM test lab. It runs batch and data-sharing applications that exploit and stress the latest functions with up to two levels of subsystems on three levels of z/OS systems. The CST team is continuously improving the test environment. For more information about the environment, see the quarterly Consolidated Service Test Report at the CST website: http://www.ibm.com/eserver/zseries/zos/servicetst/.

During testing, the team observes how each product runs and how all the products interact in this environment. The team reports problems it finds to the IBM Support Center.

The testing cycle is quarterly. The team begins each quarter by installing all service from the prior quarter and defining test scenarios to exploit new product functions while existing workloads are being run. During the second month of the quarter the team starts running new test scenarios, identifies problems, and applies fixes. In the final month of the quarter the team performs recovery tests and runs workloads in a high stress environment. At the end of the quarter the team publishes results in the Consolidated Service Test Report.

At the end of each month, between quarterly recommendations, the CST team provides a delta recommendation for customers whose preventive strategy requires more frequent maintenance updates. The monthly recommendation supports the most recently published CST quarterly recommendation. It includes HIPER and PE fixes that have been installed at the beginning of the month and tested for the duration of the month.

As quarterly and monthly recommendations become available, the team updates the CST Web site.