Destination & not defined (see long text)

What causes this issue?

There are application programs which use the specified destination for
Remote Function Calls (RFC). The destination has not been maintained and
it may be that other destinations have not been maintained either.

How to fix this error?

Ask your system administrator to do the following:

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Call the Transaction SM59.
Create destinations of type 3 (ABAP - ABAP connections) with the names
of all databases in the system (e.g. destinations C11, C20 etc.).
Specify the name of the server where the database runs. This name should
be that used in /etc/hosts for the assignment machine <-> TCP/IP
address.
Specify the number of the SAP system (usually 00). This number should be
that used in the path to the system directory (e.g.
/usr/sap/C11/DVEBMG53: system number is 53)
Create CPIC user in the target system and enter logon data with SM59.
Perform a connection test for each destination. (Caution: Logon is not
verified.)
Distribute the defined destinations (select <LS>RFC -> Distribute
entries</>.

Error message extract from SAP system. Copyright SAP SE.