Application programs can use VTAM-supplied macroinstructions to build non-LU 6.2 control blocks such as the ACB or EXLST. Application programs have many options for using macroinstructions; therefore, no macroinstructions are listed as required. VTAM® supplies macroinstructions that build control blocks at assembly time and those that allow control blocks to be built dynamically. In addition, VTAM supplies DSECT macroinstructions that enable the application program to obtain storage for a control block and use the DSECT to map the fields in the control block.

IBM® also supplies other DSECT macroinstructions, but these map control blocks are not used for LU 6.2 functions. Four of the above macroinstructions (the manipulative macrosinstructions GENCB, MODCB, SHOWCB and TESTCB) are used to create control blocks dynamically and test and set values in the control block fields. These can be used only for control blocks that are not exclusively for LU 6.2 use, such as the ACB, RPL, and EXLST. The manipulative macroinstructions do not support LU 6.2-unique control blocks such as the RPL extension for LU 6.2 or the session limits control blocks.

The declarative macroinstructions (ACB, RPL, and EXLST) build control blocks at assembly time. VTAM supplies an LU 6.2-unique declarative macroinstruction, ISTRPL6, to build the RPL extension. The other LU 6.2-unique control blocks, such as session limits control blocks, can be built from storage supplied by the application program. VTAM supplies DSECTs that enable the application program to map the storage. In addition, the APPCCMD macroinstruction includes operands that can set many of the RPL and RPL extension fields that must be initialized.