The discussion of the VTAM® LU 6.2 application programming interface (API) assumes that the reader understands certain concepts that are fundamental to LU 6.2 architecture. This section reviews those fundamental concepts. For more information, see the LU 6.2 architecture manuals: the SNA Transaction Programmer's Reference Manual for LU Type 6.2 and the SNA Format and Protocol Reference Manual: Architecture Logic for LU Type 6.2.