Determining when system definition is required
You do not have to perform a complete system definition each time a parameter value changes.
For example, you can use JCL parameters to implement some system definition changes. However, if you add application programs (excluding APPC/IMS), databases, or physical changes (excluding ETO) to the network, redefinition of the IMS system is required. Use the SYSTEM keyword of the IMSCTRL macro to define different types of system definition.
Specifying alternative versions of an online system
You can define different configurations of the IMS online system. The control modules in the nucleus and control blocks carry a one-character suffix. You specify this suffix with the SUFFIX= keyword on the IMSGEN macro. The default value is 0 (zero). The value specified for the control region parameter SUF= controls which IMS configuration is to be executed.
System definition stage 1 output
A successful stage 1 execution generates the following output:
- An extensive series of self-contained jobs.
- Warning messages, which are embedded within a listing of your input source.
- A trailer to this listing containing instructions on the content and execution of the stage 2 job stream.
Because the amount of stage 2 processing time is significant, you should review the stage 1 messages carefully. A misplaced NAME macro or misspelled LTERM name can cause service to be unavailable to an end user and require an additional stage 2 execution.
Stage 2 processing builds a control program, often called a nucleus, which is tailored according to the specifications you made in stage 1. The control program, along with most of the internal control blocks, is placed in the IMS.SDFSRESL data set.
The SYSTEM keyword on the IMSCTRL macro determines the extent of stage 2 processing.