Socket connections for IMS-to-IMS TCP/IP communications

You specify the persistence of the socket connection by using the PERSISTENT keyword of the RMTIMSCON configuration statement.

If the connection is used for MSC, the connection must be persistent. If you specify PERSISTENT=NO, IMS Connect issues a warning message and sets the value to PERSISTENT=YES.

If the connection is used for OTMA, the connection can be either persistent or non-persistent; however, to avoid the risk of a proliferation of tpipes on the remote IMS system under high-volume circumstances, specify PERSISTENT=YES.

Socket termination scenarios

When a WTOR CLOSEHWS or similar z/OS® MODIFY or IMS type-2 command is issued, IMS Connect closes all send socket connections that are in the CONN state and quiesces all send socket connections that are in the RECV state. For socket connections that are in the RECV state, IMS Connect waits indefinitely for the ACK or NAK acknowledgement from the remote IMS Connect. IMS Connect terminates only after all connections that are in the RECV state receive an acknowledgement.

When a WTOR CLOSEHWS FORCE or similar z/OS MODIFY or IMS type-2 command is issued, IMS Connect closes all send socket connections. If any send socket connections are in the RECV state, IMS Connect sends a NAK to the local OTMA and OTMA reroutes the sent messages that did not receive an acknowledgement to the timeout queue.

If IMS Connect terminates abnormally, OTMA reroutes any sent messages that did not receive an acknowledgement to the timeout queue.

For MSC socket connections, if communication with MSC stops because IMS or SCI terminated normally or abnormally, IMS Connect terminates all MSC logical links on the affected MSC physical links. IMS Connect closes all send and receive sockets used by the terminated MSC logical links. The status in IMS Connect of the affected MSC physical link is set to DISCONNECT.