Dynamic resource definition migration considerations
If you are migrating from IMS Version 13 or IMS 14, the process for enabling dynamic resource definition (DRD) in an IMS 15.2 system differs depending on whether your existing IMS system has DRD enabled. For MODBLKS resources, the process also depends on whether your resource definitions are stored in the IMSRSC repository or in the resource definition data set (RDDS).
Before enabling dynamic resource definition or shared queues, evaluate any existing DFSINSX0 exit routines. The DFSINSX0 exit might need to be changed so that it checks whether LTERM creation is allowed before it accesses the USEQDATA parameter list that is related to LTERM processing. If LTERM creation is not allowed, the USEQDATA buffer address (INSXAUSQ) is zero.
After you enable DRD, ensure that the resource definitions are no longer loaded from the IMS.MODBLKS data set and the DFSCLL3x, DFSCLR0x, and DFSCLC0x members of the IMS.SDFSRESL data set during IMS cold starts. Otherwise, if you delete runtime resources with a DELETE command and then perform a cold start using the IMS.MODBLKS data set and the DFSCLL3x, DFSCLR0x, and DFSCLC0x members for the resource definitions, those runtime resources will reappear after the next IMS cold start. For MODBLKS and MSC resources, you can either perform another system definition that omits all those resources, or hereafter start IMS without the IMS.MODBLKS data sets and the DFSCLL3x, DFSCLR0x, and DFSCLC0x members defined. For MODBLKS resources, you can use the resource definitions from the RDDS instead. MODBLKS resources can be stored in the IMS.MODBLKS data set, RDDS or the IMSRSC repository, while MSC resources can be stored in the DFSCLL3x, DFSCLR0x, and DFSCLC0x members or the IMSRSC repository.
If resources need to be changed during migration, perform a MODBLKS online change operation or the system generation process for MSC resources on the IMS systems that have not migrated to DRD. Then, issue CREATE, UPDATE, and DELETE commands as necessary on the IMS systems that have migrated to DRD.