3467221 - Error in phase RUN_RSPTBFIL_PREP_PUTTB: failed with code 1 key RFC_COMMUNICATION_FAILURE: Timeout while opening an RFC connection.

System upgrade fails in SUM phase PREP_SHDTABLES/RUN_RSPTBFIL_PREP_PUTTB with below error:

Last generated error message:
RFC login to system (SID) ashost XXXX  nr XX gwhost XXXX gwservice XXXX
failed with code 1 key RFC_COMMUNICATION_FAILURE: Timeout while opening an RFC
connection.

Error: Batchjob 'RSPTBFIL' with id 'XXXXX' is aborted.

Abstract of log file 'log\PHASE_RUN.LOG':

2 ETQ399 20240508102807: Job RSPTBFIL jobcount 10274400 still running.
2 ETQ399 20240508102810: Job RSPTBFIL jobcount 10274400 still running.

..........

2WETQ399 RFC for SUBST_CHECK_BATCHJOB failed, try again after 10 seconds.
1 ETQ359 RFC Login to: System="SID", AsHost="XXXX" Nr="XX", Client="XXX", User="DDIC", GwHost="XXXX", GwService="XXXX"
2EETQ231 RFC Login failed
1EETQ399 Last generated error message is: RFC login to system SID ashost "XXXX" nr "XX" gwhost "XXXX"
1EETQ399Xgwservice "XXXX" failed with code 1 key RFC_COMMUNICATION_FAILURE: Timeout while opening an RFC
1EETQ399Xconnection.
1EETQ204 Upgrade phase "RUN_RSPTBFIL_PREP_PUTTB" terminated with severe errors ("20240508104436")

SAP NetWeaver.

SAP S/4HANA

SUM 2.0

SUM ERROR, PREP_SHDTABLES/RUN_RSPTBFIL_PREP_PUTTB, PHASE_RUN.LOG, Job count, RFC_COMMUNICATION_FAILURE, Timeout while opening an RFC. , KBA , BC-UPG-DTM-TLA , Downtime Minimization for ABAP , Problem