Conversion and Migration Aid for IMS
IMS Database Migration Aid (DMA)

Changes to the structure of IMS data usually involve a change of related programs. The complete conversion of a particular date in a so called big bang – the activation of all modified programs, jobs, etc. with the modified data structure – is normally difficult to realize. Stepwise conversion on the other hand leads to the problem of how “old” programs (i.e. not yet converted programs) can deal with the “new” data structure, or vice versa, how can already converted programs work with “old” data?

DMA-IMS Database Migration Aid allows a gradual or packet-wise migration by dynamically presenting the data to the respective program as required. New programs “see” the new data structure, old programs the old structure. DMA switches the “view” dynamically, based on a rule set. Already converted programs work with converted data. Not yet converted programs don’t see any change and work as usual.

DMA simplifies the embedding of new fields and the modification of existing fields in IMS databases without alteration of DBDs and PSBs.

Image DMA

DMA provides support for:

  • changes to key fields
  • changes to search arguments (SSAs)
  • changes to feedback areas
  • changes to segment data areas
  • version support for program and database (old/new, versions)
  • field dependent segment layout (record types)

Definition process:

  • The affected segments are identified by the user.
  • The programs affected are detected by IMS Migration Aid via DBDs and PSBs/ACBs.
  • The required information is taken from IMS control blocks and included in the Migration Aids database.
  • Base definitions are done automatically.
  • The segment layout taken from the IMS DBD definitions may be completed by the inclusion of PL/I and COBOL structures.
  • The actual conversion between versions is done by routines that are either provided by the system or written by the user. (rule routines)

The problem addressed by DMA obviously has to do with ‘versioning’. With Version 13 IMS provides ‘Versioning Support’. Unfortunately, in most cases the features offered are insufficient.