A PL/I host structure name can be a structure name with members that are not structures or unions. For example:
dcl 1 A,
2 B,
3 C1 char(...),
3 C2 char(...);
In this example, B is the name of a host structure consisting of the scalars C1 and C2.
Host structures are limited to two levels. A host structure can be thought of as a named collection of host variables.
Each leaf element of a host structure must have one of the following valid host data attributes as discussed in Declaring host variables: