Modifying the system design

The need for changes can result from:

• The integration of new applications
• The staged implementation of an application package
• Modifications to an application design already in production
• Modifications to the network if ETO is not used
• Maintenance of the IMS system at the current level and incorporation of fixes for application program problems
• Tuning of system control parameters
• Redistribution of database data sets
• Storage device changes

All of these changes can affect the IMS system definition and necessitate building a new nucleus and control blocks. The last two changes might only require JCL changes and database reorganization. However, the repercussions can be widespread. With any design change, it is important to control its implementation in order to protect the existing system and the needs of all end users. Implementation of most changes to a production system is best handled by prior testing and a carefully monitored validation period.

The task of administering a change to your IMS online system is likely to involve the following activities:

• Reallocating IMS system data sets and updating execution libraries
• Performing the appropriate system definition tasks
• Reviewing security arrangements, adding changes to RACF® user, group, and resource profiles
• Documenting changes in operating procedures
• Documenting changes in recovery procedures
• Being aware of the testing strategy and the timing of cutover into production mode
• Analyzing the performance impact and revising predictions
• Coordinating the use of the IMS Monitor and otherwise monitoring the system before and after implementation
• Collecting comparative performance data