For PACKED-DECIMAL there are 2 digits for each character position, except for the trailing character position, which is occupied by the low-order digit and the sign. Such an item can contain any of the digits 0 through 9, plus a sign, representing a value not exceeding 18 decimal digits.
COMP-3 to NUMERIC NO....as since it contains sign fields, it can give S0C7
NUMERIC to COMP-3 YES
COMP-3 to COMP NO....Higher range to Lower range data movement is not possible
COMP to COMP-3 YES
I am not too sure about this thing.
Will get back to you.
I'm not aware of any restrictions on moves from one numeric data type to another, provided that the field lengths are adequate to accommodate conversion of the digits (e.g.. 123C to F1F2C3). Unless I'm misreading what you wrote.
You can do the kind of redefine you mentioned, but you have to be very careful when you use the field (I wouldn't reccommend it). You must be aware of the kind of data that is in the field at the time you use it. For example, if you moved packed data in at some point but then forget and attempt to move it out using the COMP field name, the data conversion will be wrong causing an 0C7 when the receiving field is used in an arithmetic expression.
Another caution when doing that kind of redefines: you must define both fields so that they are the same length (NOT the same number of 9s).