After upgrading to BC 7.2, the interior and gateway server are up and running but seeing many JMX errors as below in the IS logs :
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2020 Mar 24 10:22:58:163 GMT +0100 BW.BusinessConnect-Interior_Server-B2B2 Error [bw.logger] BW-EXT-LOG-100000  (BCPartnerCommunity) Error processing Gateway startup. Error connecting via JMX to Gateway.: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is: 
    iaik.security.ssl.SSLException: Peer sent alert: Alert Fatal: handshake failure]: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is: 
    iaik.security.ssl.SSLException: Peer sent alert: Alert Fatal: handshake failure] 
2020 Mar 24 10:22:58:163 GMT +0100 BW.BusinessConnect-Interior_Server-B2B2 Error [bw.logger] BW-EXT-LOG-100000  Error connecting via JMX to Gateway.: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is: 
    iaik.security.ssl.SSLException: Peer sent alert: Alert Fatal: handshake failure]: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is: 
    iaik.security.ssl.SSLException: Peer sent alert: Alert Fatal: handshake failure]
    at com.tibco.ax.gs.mgmt.runtime.GSActivity.messengerIdleAck(GSActivity.java:324)
    at com.tibco.ax.gs.mgmt.runtime.GSActivity.sDispatchMessengerRequest(GSActivity.java:73)
    at com.tibco.ax.tcm.model.impl.TCMActivity.sDispatchRequest(TCMActivity.java:206)
    at com.tibco.ax.tcm.model.impl.TCMActivity.sProcessRequest(TCMActivity.java:109)
    at com.tibco.ax.tcm.gateway.runtime.TcmInboundBMHService.validateAndConvertDocument(TcmInboundBMHService.java:91)
    at com.tibco.ax.fw.runtime.inbound.impl.IBBMHService.validateDocument(IBBMHService.java:583)
    at com.tibco.ax.fw.runtime.inbound.impl.IBBMHService.preProcessMsg(IBBMHService.java:217)
    at com.tibco.ax.fw.runtime.impl.AbstractService.preProcessor(AbstractService.java:291)
    at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.tibco.plugin.gateway.InvokeOperationActivity.sInvokeServiceOp(InvokeOperationActivity.java:246)
    at com.tibco.plugin.gateway.InvokeOperationActivity.eval(InvokeOperationActivity.java:129)
    at com.tibco.pe.plugin.Activity.eval(Unknown Source)
    at com.tibco.pe.core.TaskImpl.eval(Unknown Source)
    at com.tibco.pe.core.Job.a(Unknown Source)
    at com.tibco.pe.core.Job.k(Unknown Source)
    at com.tibco.pe.core.JobDispatcher$JobCourier.a(Unknown Source)
    at com.tibco.pe.core.JobDispatcher$JobCourier.run(Unknown Source)
...
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The IS logs indicate that a previous version (Entrust) of the security classes are being used.  BC 7.2.0 uses the Bouncy Castle security library. The exception indicates that the BC installation is using an incorrect TRA or that it is configured incorrectly.
 

All environments

Make sure of the below two things :
1. If you refer to BC 7.2.0 readme, you will see the below :
    <<<
            Minimum Software Requirements :
                    TIBCO Runtime Agent(TM) 5.10.2

            TIBCO Product Compatibilities : 
                     TIBCO Runtime Agent(TM) 5.10.2 - 5.11.x
                     (Excluded Versions: 5.11.0)
    >>>
Please insure that the correct version of the TRA is installed.

2.  Under BusinessConnect > System Settings > Activated Protocol Plug-ins and Properties > BC, set :
      "Outgoing secure sockets vendor" = SUN
 

When using BusinessConnect 7.2.0, the Gateway Server (GS) and Interior Servers (IS) are starting, but a large number of IAIK exceptions are seen in the in the IS logs.

JMX, IAIK, TRA, Entrust, Bouncy Castle