HLASM: V1R6 Language Ref

DROP instruction..INREC DS CL156OUTREC DS CL156In the above example, the DROP instruction makes the labels PRIOR and POSTunavailable as symbol qualifiers.When a labeled dependent USING domain is dropped, none of any subordinateUSING domains are dropped. In the following example the labeled dependentUSING BLBL1 is not dropped, even though it is dependent on the USING ALBL2that is dropped:USINGDSECTA,14ALBL1 USING DSECTA,14USINGDSECTB,ALBL1.A..ALBL2 USING DSECTA,ALBL1.A.BLBL1 USING DSECTA,ALBL2.A+4.DROPALBL2.DSECTA DSECTA DS ADSECTB DSECTB DS AA DROP instruction is not needed:v If the base address is being changed by a new ordinary USING instruction, andthe same base register is assigned. However, the new base address must beloaded into the base register by an appropriate sequence of instructions.v If the base address is being changed by a new labeled USING instruction or anew labeled dependent USING instruction, and the same USING label isassigned; however, the correct base address must be loaded into the base registerspecified in the USING instruction by an appropriate sequence of instructions.v At the end of a source moduleDSinstructionThe DS instruction:v Reserves areas of storagev Provides labels for these areasv Uses these areas by referring to the symbols defined as labelsv If a control section has not previously been established, DS will initiate anunnamed (private) control section►►symbolDS ▼ ,operand►◄symbolis one of the following:Chapter 5. Assembler instruction statements 173