The error message is due to checks made when using SIMPLIFY mode. This is activated in DBSIDPR with SIMPLIFY_MODE=YES.
The problem is the dastaset name of the CXX does not match the pattern specified in the DBSIDPR DSN_XXX= parameter.
This parameter also applies to the dataset names of the LXX, and FXX so the error message could also refer to the LXX or FXX.
For example in this message:
DB01409E - DATA SET NAME MISMATCH CXX-DATACOM.R14.MUF2.CXX DBSIDPR-DATACOM.R15.MUF2.CXX
It means in DBSIDPR you coded DSN_XXX=DATACOM.R15.MUF2.???
So the CXX has to be named DATACOM.R15.MUF2.CXX but it is named DATACOM.R14.MUF2.CXX