Here gives an example about how to use the PARTITION function.
SELECT PARTITION(CORPDATA.EMPLOYEE), LASTNAME FROM CORPDATA.EMPLOYEE
OPNQRYF FILE((CORPDATA/EMPLOYEE)) FORMAT(FNAME) MAPFLD((PART1 '%PARTITION(1)'))
SELECT EMPNO FROM CORPDATA.EMPLOYEE WHERE PARTITION(CORPDATA.EMPLOYEE) = 100
OPNQRYF FILE((EMPLOYEE)) QRYSLT('%PARTITION(1) *EQ 100')
SELECT * FROM CORPDATA.EMPLOYEE X, CORPDATA.DEPARTMENT Y WHERE PARTITION(X)=PARTITION(Y)
OPNQRYF FILE((CORPDATA/EMPLOYEE) (CORPDATA/DEPARTMENT)) FORMAT(FNAME) JFLD((1/PART1 2/PART2 *EQ)) MAPFLD((PART1 '%PARTITION(1)') (PART2 '%PARTITION(2)'))