Each function has from two to four parameters.

The first parameter must be a Session Control Block. This structure contains information used by the upper layers of the DBMS data type subsystem. Inside the Session Control Block is a structure named scb_error of the type II_ERR_STRUCT. Structure scb_error must be filled in when the function returns an error.

The last parameter must be a pointer to a result of some type. The result structure can be a single element, such as an integer, containing some sort of indicator, but most often it is an II_DATA_VALUE (defined below).

The result can contain valid data that specifies some portion of the work to be done. This is often done when the routine is creating a portion of a value and another portion of the value is created elsewhere. For example, this is done if getempty() was providing the data and the actual type and length were being created elsewhere.

The two optional parameters (arg1 and arg2) are pointers to II_DATA_VALUE (see Structure II_DATA VALUE) structures that describe the data values manipulated by the routine. Each function uses II_DATA_VALUE structures.