If a catalog is defined in the CATALOG parameter, that catalog
is selected to contain the to-be-defined entry.
When a non-VSAM generation data group (GDG) data set is defined,
the catalog containing the GDG base is selected to contain the to-be-defined
non-VSAM entry.
If no user catalog is specified for the current job step or job,
the entry's name is a qualified name, and:
One or more of its qualifiers is the same as the name or the alias
of a catalog, or
The first qualifier is the same as the name or the alias of a
VSAM user catalog,
then the catalog so identified is selected to contain the to-be-defined
entry.
If no catalog has been identified, either explicitly or implicitly,
VSAM defines an object in the master catalog.