The common parameters listed in Common Parameters are
always required. Most service calls have additional parameters, and
most of them are required, but a few parameters are listed as optional.
An optional parameter may be shown as omitted in one of three ways:
- If no parameters follow it, by passing a short parameter list.
As noted earlier, all parameter lists are to be constructed in the
VL or varying length form.
- Providing binary zero in place of an address
in the parameter list.
- By passing a null value. The null value for a varying length character
string such as SECTION, is a zero-length string. The null value for
fullword or doubleword parameters is a fullword or doubleword of binary zero.