Comparison rules

The following rules apply to comparisons:

For a comparison to be valid, one operand must either be a read-only variable or a read-write variable and the other operand must be a constant (any of the four types), a read-only variable, or a FILTLIST name.
Numerics are right justified.
Literals are left justified and padded with blanks.
Type checking is done to ensure that numeric read-only variables are not being compared to characters (literals) and that character (literal) read-only variables are not being compared to numbers. &NQUAL, &NVOL, &SIZE, &MAXSIZE &MEMNQUAL and &RETPD are the only numeric read-only variables.
Limited length checking of read-only variables with their maximum length values is performed to ensure that the maximum lengths are not exceeded. For example, the literal to which &DSN is being compared must be no longer than 44 characters. See Read-only variables for maximum lengths.