An IF command in a THEN or ELSE clause is a nested IF command. The maximum level of nesting is 10, starting with the first time you specify IF.

Within a nest of IF commands, the innermost ELSE clause is associated with the innermost THEN clause, the next innermost ELSE clause with the next innermost THEN clause, and so on. If there is an IF command that does not require an ELSE clause, use a null ELSE clause (see Creating a null command), unless the nesting structure does not require one. If a nesting structure does not require a null ELSE clause, the DFSMSdss job stream tells you.