On the mainframe, there are two frequent causes of operational errors:
The IMS TM or SNA operator put the resource out of service with the vary command.
SNA placed the line, physical unit (PU), or LU into a non-operating (INOP) state because of a network outage.
In these cases, either:
The TRS administrator sees SNA Services timeout and connection failure messages when he or she tries to start the DirectConnect for z/OS Option, or
The requesting client sees an SNA Services message indicating that the system could not start the RPC.
When you are contacted about such messages, reactivate the necessary mainframe resources.
