Allocating the RECON data sets

For both online and batch DBRC jobs, you can allocate the RECON1, RECON2, and RECON3 data sets with JCL, or you can let DBRC dynamically allocate them.

When dynamically allocating the RECON data set, omit the DD statements for RECON1, RECON2, and RECON3.

Use the TYPE=RECON macro statement of the IMS DFSMDA dynamic allocation macro to establish three dynamic allocation parameter lists in IMS.SDFSRESL. When multiple processors access the same RECON data sets, keep the IMS.SDFSRESL information pertaining to dynamic allocation parameters in synchronization on all processors.

Related reading: See IMS Version 15.6 System Definition for information about the DFSMDA macro.

DBRC always allocates RECON data sets with DISP=SHR.

Although JCL allocation and dynamic allocation are both valid methods for allocating RECON data sets, JCL allocation should be used only in a controlled test.

Recommendation: Use dynamic allocation for your production system and all other test or development environments.

The principal advantages of dynamically allocating the RECON data set are:

All DBRC jobs automatically use the correct and current RECON data sets, and no JCL statements are left to become outdated.
You can reorganize and restore RECON data sets, in case of error, without having to shut down online IMS systems.

Requirement: When accessing the RECON data sets in parallel mode, they must be managed by DFSMS.