You can pass *OMIT for a prototyped parameter if the called procedure is aware that *OMIT might be passed. In other words, you can pass *OMIT if the keyword OPTIONS(*OMIT) is specified on the corresponding parameter definition in the prototype. When *OMIT is specified, the compiler will generate the necessary code to indicate to the called procedure that the parameter has been omitted.
To determine if *OMIT has been passed to an ILE RPG procedure, use the %ADDR built-in function to check the address of the parameter in question. If the address is *NULL, then *OMIT has been passed. You can also use the CEETSTA (Check for Omitted Argument) bindable API. (See Figure 67 for a brief example.)
The following is a simple example of how *OMIT can be used. In this example, a procedure calls the ILE bindable API CEEDOD in order to decompose an operational descriptor. The CEEDOD API expects to receive seven parameters; yet only six have been defined in the calling procedure. The last parameter of CEEDOD (and of most bindable APIs) is the feedback code which can be used to determine how the API ended. However, the calling procedure has been designed to receive any error messages via an exception rather than this feedback code. Consequently, on the call to CEEDOD, the procedure must indicate that the parameter for the feedback code has been omitted.
See Sample Service Program for an example of using *OMIT.