STOP

The character string STOP tells FM/Db2 to stop the current FM/Db2 function after the current record has been written to the primary output data set. Specifying STOP on the RETURN instruction results in the current record being imported to the target table and the Import utility being stopped.

Here are some examples:
RETURN 'STOP'
Return 'Stop'
Return stop  /* assumes no variable named 'stop' has been assigned */