The "ONE SIZE ERROR" option in error trapping is used to handle arithmetic errors in COBOL programs. When this option is specified, it allows the program to continue execution even if an arithmetic error occurs during a calculation. Instead of immediately terminating the program, the error condition is noted, and the erroneous result is replaced with an implementation-defined value.
Using the "ONE SIZE ERROR" option can be beneficial in situations where minor arithmetic errors may occur. The program can still proceed with its intended functionality without halting. However, it is crucial to handle these errors appropriately to prevent unintended consequences or data inconsistencies in the program's output.