Define an external procedure

Consider the following example:

 CREATE PROCEDURE P1
          (INOUT PARM1 CHAR(10))
          EXTERNAL NAME MYLIB.PROC1
          LANGUAGE C
          GENERAL WITH NULLS
 

This CREATE PROCEDURE statement:

• Names the procedure P1
• Defines one parameter which is used both as an input parameter and an output parameter. The parameter is a character field of length ten. Parameters can be defined to be type IN, OUT, or INOUT. The parameter type determines when the values for the parameters get passed to and from the procedure.
• Defines the name of the program which corresponds to the procedure, which is PROC1 in MYLIB. MYLIB.PROC1 is the program which is called when the procedure is called on a CALL statement.
• Indicates that the procedure P1 (program MYLIB.PROC1) is written in C. The language is important since it impacts the types of parameters that can be passed. It also affects how the parameters are passed to the procedure (for example, for ILE C procedures, a NUL-terminator is passed on character, graphic, date, time, and timestamp parameters).
• Defines the CALL type to be GENERAL WITH NULLS. This indicates that the parameter for the procedure can possibly contain the NULL value, and therefore will like an additional argument passed to the procedure on the CALL statement. The additional argument is an array of N short integers, where N is the number of parameters that are declared in the CREATE PROCEDURE statement. In this example, the array contains only one element since there is only parameter.

It is important to note that it is not necessary to define a procedure in order to call it. However, if no procedure definition is found, either from a prior CREATE PROCEDURE or from a DECLARE PROCEDURE in this program, certain restrictions and assumptions are made when the procedure is called on the CALL statement. For example, the NULL indicator argument cannot be passed.