Establishing and controlling SNA sessions

Logical units (LUs) are defined to VTAM® to provide access services to network resources. To tailor sessions, VTAM uses the unformatted system service (USS), interpret, logon mode, and Class of Service tables. VTAM also uses the logon-interpret routines and the virtual route selection and session management exit routines to authorize, establish, or terminate sessions. You can replace or modify these tables and routines. This, along with operands that can be specified in VTAM definitions, allows VTAM to adapt to your needs. The z/OS Communications Server: SNA Resource Definition Reference describes how to replace or modify the tables used in session establishment and termination and how to specify the network definition operands that relate to sessions. z/OS Communications Server: SNA Programming describes how VTAM initiates, controls, and terminates sessions. z/OS Communications Server: SNA Customization describes the exit routines.

Sessions between LUs can be initiated by the following actions:
  • Session-initiation requests from a logical unit
  • Automatic logon
  • The application program using API requests (for example, OPNDST, SIMLOGON, or REQSESS)
  • The VTAM operator using, for example, VARY LOGON commands
Normally, sessions are terminated by one of the following actions:
  • Session-termination requests from an LU
  • The application program using API requests (for example, CLSDST or TERMSESS)
  • The VTAM operator, using VARY resource deactivation commands
z/OS Communications Server: SNA Programming describes the use of VTAM application programming interface (API) macros to establish and terminate sessions.
The following list shows where to find more information about establishing and controlling SNA sessions.