Using Temporary Variable in FIXParallel

While reading the blogs and forums on using temporary variables in Fix Parallel, I was under the impression that there is no change the way we use it. But I was getting following error when I used to use temp var the same way we used it in FIX command:

"FIXPARALLEL (line 99): Modify the VAR variable inside FIXPARALLEL command Rule"

 However after doing through the documentation and few testing, I found that it's not the case.

Following is the example how we use the temporary variable in FIX command:

VAR V_Period_Start = 20160101;
VAR V_Period_End = 20161231;
VAR V_TotalDays = 0;

FIX(@RELATIVE("Entity_1",0),
        "Budget",
        &WFBudYr
    )
    "Working"
    (
        V_TotalDays = @CalcMgrDateDiff(V_Period_Start, V_Period_End, "day") + 1;

        @RETURN(@CalcMgrDoubleToString (V_TotalDays),INFO);
)
ENDFIX;

Note above that we can declare the variable before the FIX and we can also initialize with a value while declaring. However this is not the case when using the variable (in similar way as above) in FIXParallel command.

Using FIXParallel it can be written as follows:

FIXPARALLEL(8,@RELATIVE("Entity_1",0),
            "Budget",
            &WFBudYr
    )
    THREADVAR V_Period_Start;
    THREADVAR V_Period_End;
    THREADVAR V_TotalDays;

    "Working"
    (
        V_Period_Start = 20160101;
        V_Period_End = 20161231;
        V_TotalDays = @CalcMgrDateDiff(V_Period_Start, V_Period_End, "day") + 1;
       
        @RETURN(@CalcMgrDoubleToString (V_TotalDays),INFO);
)
ENDFIXPARALLEL;

As you can see, when using temp variable within FIXPARALLEL, it must be declared inside the FIXPARALLEL block with the keyword "THREADVAR". Also note that you cannot initialize with any value while declaring the variable.