Declare a type for internal table IT_MKPF which will have type of USNAM same as USRID.
TYPES: BEGIN OF TY_MKPF,
MANDT TYPE MKPF-MANDT,
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USNAM TYPE PA0105-USRID,
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END OF TY_MKPF.
DATA: IT_MKPF TYPE STANDARD TABLE OF TY_MKPF,
WA_MKPF TYPE TY_MKPF.