DFSDSCMx member of the IMS PROCLIB data set

When the Extended Terminal Option (ETO) is enabled, IMS generates ETO descriptors during stage 1 system definition and stores them in the DFSDSCMx member of the IMS.PROCLIB data set.

IMS generates both default descriptors and descriptors that are based on any static definitions in the IMS stage-1 system definition macros. The types of descriptors that IMS can generate include logon descriptors, MFS device descriptors, MSC descriptors, and user descriptors.

Recommendation: If you code your own descriptors, do not store them in the DFSDSCMx member. The contents of the DFSDSCMx member are deleted and regenerated each time a stage 1 system definition is performed. To preserve descriptors that you code across a stage-1 system definition, store them in the DFSDSCTy member of the IMS.PROCLIB data set.

The x on DFSDSCMx is the IMS nucleus suffix. The suffix must match a suffix that your installation specifies on the SUFFIX= parameter of the IMSGEN system definition macro.

To use IMS ETO, at least one user descriptor and one logon descriptor must exist. If at least one of each of these descriptors does not exist or cannot be found when you enable IMS ETO, IMS abends with U0015 issuing message DFS3652.

The following rules apply to creating ETO descriptors:

  • Separate one keyword or parameter set from another with one or more blanks.
  • Do not include embedded blanks within a keyword and its parameters.
  • Separate a keyword from its parameters with an equal sign (=).
  • Do not abbreviate keywords.

You can continue a keyword and its parameter set to the next statement if no intervening blanks appear at the end of the first statement or at the beginning of the parameters of the next statement. A continued statement still has the same descriptor type and name in columns 1-10; the continued specification begins in column 12. If you specify keywords, they must be accompanied by parameters. Keywords followed by blanks or commas are invalid.

The format and parameters of the ETO descriptors are described in the following topics: