Sometimes when you are running a CONNECT statement from Interactive SQL, a general SQ30080 message is given.
The text of that message is:
Communication error occurred during distributed database processing
In order to get the details of the error, you should exit from Interactive SQL and look at the job log.
If you get message SQL7020, SQL package creation failed, when connecting for the first time (for any given level of commitment control) to a server that has only single-phase commit capabilities, the cause might be that you accessed the remote server as a read-only server and you need to update it to create the SQL package.
You can verify that by looking at the messages in the job log. The solution is to do a RELEASE ALL and COMMIT to get rid of all connections before connecting, so that the connection will be updatable.