z/OS® Communications Server restricts how multiple EE connections are established between two EE endpoints.

When establishing multiple EE connections between the same two EE endpoints (parallel EE connections), you cannot use the same IP address pair for more than one EE connection. Instead, every EE connection must use a unique IP address pair. You can define parallel EE connections by using a different local static VIPA address or remote IP address (or both) for each connection. z/OS Communications Server does not prevent parallel EE connections from being established as long as each connection uses a unique IP address pair. There is no limit to the number of EE connections that can be established using unique IP address pairs.

Before V1R8, an alternate method allowed parallel EE connections between the same IP address pair. As of V1R8, the initiation of parallel EE connections between the same IP address pair is no longer supported. This restriction applies only to parallel EE connections that are initiated by VTAM®. An inbound parallel EE connection request, that uses the same IP address pair and different SAP values, will be accepted by VTAM.