The relevant language in the z/OS MVS JCL Reference is
<begin snippet>
The IF statement is always followed by a relational-expression and a
THEN clause.
Optionally, an ELSE clause can follow the THEN clause. An ENDIF
statement
always follows the ELSE clause, if present, or the THEN clause.
v The THEN clause specifies the job steps that the system
processes when the
evaluation of the relational-expression for the IF statement is a
true condition.
The system evaluates the relational-expression at execution time.
v The ELSE clause specifies the job steps that the system
processes when the
evaluation of the relational-expression for the IF statement is a
false condition.
v The ENDIF statement indicates the end of the IF/THEN/ELSE/ENDIF
statement
construct, and must be coded for each construct.
You can nest IF/THEN/ELSE/ENDIF statement constructs up to a maximum
of 15
levels. The steps that execute in a THEN clause and an ELSE clause
can be
another IF/THEN/ELSE/ENDIF statement construct.
</end snippet>
Worth emphasizing and important when nesting is used is that either of THEN
and ELSE can be vacuous or empty.
The constructs
|// IF <relational expression> THEN
|// ELSE
|// . . .
|// ENDIF
and
|// IF <relational expression> THEN
|// . . .
|// ELSE
|// ENDIF
are both usable.
Moreover, FORTRAN and C programmers who have an emotional need to put
parentheses around <relational expression> may do so [without, however,
omitting the following THEN].
The construct
|// IF RC ¬= 0 THEN
|// ELSE
|// . . .
|// . . .
|// ENDIF
thus flushes whatever is bracketed by ELSE and ENDIF when a non-zero return
code obtains.
John Gilmore Ashland, MA 01721-1817 USA
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