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:
USING DSECTA,14
ALBL1 USING DSECTA,14
USING DSECTB,ALBL1.A
.
.
ALBL2 USING DSECTA,ALBL1.A
.
BLBL1 USING DSECTA,ALBL2.A+4
.
DROP ALBL2
.
DSECTA DSECT
A DS A
DSECTB DSECT
B DS A
A DROP instruction is not needed:
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