HLASM Language Reference

DROP Instruction
DROP 7,11
DROP
FIRST
Labeled USING: You cannot end the domain of a labeled USING instruction by
coding a DROP instruction that specifies the same registers as were specified in
the labeled USING instruction. If you want to end the domain of a labeled USING
instruction, you must code a DROP instruction with an operand that specifies the
label of the labeled USING instruction.
Dependent USING: To end the domain of a dependent USING instruction, you
must end the domain of the corresponding ordinary USING instruction. In the
following example, the DROP instruction prevents the assembler from using register
12 as a base register. The DROP instruction causes the assembler to end the
domain of the ordinary USING instruction and the domains of the two dependent
USING instructions. The storage areas represented by INREC and OUTREC are both
within the range of the ordinary USING instruction (register 12).
USING ,12
USING
RECMAP,INREC
USING
RECMAP,OUTREC
.
.
DROP 12
.
.
INREC DS CL156
OUTREC DS CL156
To end the domain of a labeled dependent USING instruction, you can code a
DROP instruction with the USING label in the operand. The following example
shows this:
USING ,12
PRIOR USING RECMAP,INREC
POST USING RECMAP,OUTREC
.
.
DROP
PRIOR,POST
.
.
INREC DS CL156
OUTREC DS CL156
In the above example, the DROP instruction makes the labels PRIOR and POST
unavailable as symbol qualifiers.
When a labeled dependent USING domain is dropped, none of any subordinate
USING domains are dropped. In the following example the labeled dependent
USING BLBL1 is not dropped, even though it is dependent on the USING ALBL2 that
is dropped:
Chapter 5. Assembler Instruction Statements 173