1974139 - Message server disconnection error while system works fine

After system upgrade, for example Unicode conversation or applying a newer Support Package (SP), the below error appears in the Dispatcher trace file (/usr/sap/<SYS>/<instance name>/work/dev_disp):

And in the Message Server trace file (/usr/sap/<SYS>/<instance name>/work/dev_ms), the following can be seen during the same timestamp:

• Where C1 (xxx_<SID>_<NR>) is the real existed instance which reporting the above error in the dev_disp trace,
• inv_name xxx_<SID>_<NR> is the source system,
• The error does not have any application impacts, the system is working fine and connection between the message server and the dialog instance is also fine,
• All instances in the transaction SM51 are active, though the above error happens every time after starting the system.

• Operating System independent
• Database independent
• SAP NetWeaver
• SAP Web Application Server for SAP S/4HANA
• ABAP Platform

RZ04, MSEPARTNERUNKNOWN, send inv_name, system upgrade, Unicode conversation, Support Package (SP), /usr/sap/<SYS>/<instance name>/work/dev_disp, Message Server, /usr/sap/<SYS>/<instance name>/work/dev_ms, SM51, RZ04, operation mode switch, old instance, RZ12, RFC logon group, INSTANZNAME , KBA , BC-CST-MS , Message Service , Problem