Vector lists provide an open-ended interface for application programs to exchange information with VTAM®. Each vector list contains a 2-byte length field followed by a set of contiguous vectors in random order, as shown in Figure 1.

Each vector in the vector list is a set of contiguous data containing a length field, an identifier, and a value field containing vector data. The fields containing vector data can have trailing blanks. Some vector lists are built before or during OPEN processing, while others are built during processing of the APPCCMD macroinstruction.  Table 1 shows the vector lists available to VTAM applications, the macroinstruction with which they are associated, and their function.