IMS dynamic allocation macro (DFSMDA)

Use the IMS dynamic allocation macro (DFSMDA) in all production databases.

Use DFSMDA in all production databases for the following reasons:
  • Allocation is controlled from a central point.
  • You do not have to change DBCTL JCL or batch job JCL to change a data set name.
  • It avoids possible confusion over which DBCTL address space requires the DD statement for a database, because the library with the DFSMDA members can be concatenated in the STEPLIB DD statement.
  • If you do not use DFSMDA, DL/I database DD statements must be in the DLISAS (DLS) address space, and DEDB DD statements must be in the DBCTL (DBC) address space.

To use dynamic allocation, you need one member per database in the IMS.RESLIB library (or an authorized STEPLIB library), using the IMSDALOC procedure to assemble and link-edit the appropriate DFSMDA macros. See IMS: System administration for general guidance on dynamic allocation and IMS reference: Database utilities for guidance on using the DFSMDA macro.