Host variables can be qualified using DB2 for MVS compatible syntax.
For example, suppose you have defined some host variables as follows:
01 block-1. 03 hostvar pic s9(4) comp-5. 01 block-2. 03 hostvar pic s9(4) comp-5.
You can qualify which instance of hostvar to use with syntax of the form:
exec sql fetch s2 into :block-1.hostvar end-exec