Using the VTAM application programming interface
The VTAM® application program interface (API) used by IMS for ISC consists of macro instructions and control blocks.
- Establish connection or disconnection.
- Request and control the transfer of data between IMS and another logical unit.
To provide application-to-application communication, the VTAM API provides both a primary and a secondary session application interface. The primary interface is essentially the same as that used by IMS to support other VTAM nodes. However, the interface introduces some new macros and some additional parameters on existing macros.
The VTAM API supports single sessions as well as parallel (multiple, simultaneously active) sessions between two logical units. The IMS interface for this support is primarily through the session qualifier fields of CINIT and BIND, which are available through the LOGON and SCIP exit routines. Single-session support requires static definition of message queues during IMS system definition; parallel-session support permits message queues to be dynamically allocated at session initiation.
For more information about VTAM, see z/OS® Communications Server: SNA Resource Definition Reference.