The maximum size of each operand is 18 decimal digits.
The maximum size of a zoned decimal or an internal decimal operand is 63 decimal digits.
From each operand, you can determine the number of decimal digits in the composite of operands. The composite of operands is a hypothetical data item resulting from aligning the operands at the decimal point and then superimposing them on one another.
A PICTURE 9(7)V9(5).
B PICTURE 9(11)V99.
C PICTURE 9(12)V9(3).
ADD A B TO C
Composite-of-Operands PICTURE 9(12)V9(5).
If the composite of operands is 18 digits or less, enough places are carried so that no significant digits are lost during execution.
When the (default) compiler option *NOEXTEND or the PROCESS statement option NOEXTEND is specified, the composite of operands can have a maximum length of 30 decimal digits.
The composite of operands can have a maximum length of 31 decimal digits when the arithmetic mode compiler option *EXTEND31 or PROCESS statement option EXTEND31 is specified.
The
composite of operands can have a maximum length of 34 decimal digits
when the arithmetic mode compiler option *EXTEND31FULL or PROCESS
statement option EXTEND31FULL is specified. 
The composite of operands can have a maximum length of 63 decimal digits when the arithmetic mode compiler option *EXTEND63 or PROCESS statement option EXTEND63 is specified.
The following table shows the maximum number of decimal digits that are allowed for the composite of operands in arithmetic statements.
| Compiler Option/Process Statement | Maximum Length of Composite (decimal digits) |
| *NOEXTEND/NOEXTEND | 18 IBM Extension 30 End of IBM Extension |
| *EXTEND31/EXTEND31 | 18 IBM Extension 31 End of IBM Extension |
*EXTEND31FULL/EXTEND31FULL ![]() |
IBM Extension 34 End of IBM Extension |
| *EXTEND63/EXTEND63 | IBM Extension 63 End of IBM Extension |
The following list shows how the composite of operands is determined for arithmetic statements:
In all arithmetic statements, it is important to define data with enough digits and decimal places to ensure the desired accuracy in the final result. For more information on arithmetic precision, see Appendix B. Intermediate Results and Arithmetic Precision.