Have you tried RCLRSC?
I looked up that message ID and read its message text.
Message . . . . : Connection to relational database &1 already exists.
Cause . . . . . : An attempt was made to do one of the following:
-- CONNECT to a relational database when the connection is active.
-- CONNECT to a relational database that has the same communication
information as a connection to a relational database that is active.
The active relational database is &1.
Recovery . . . : If CONNECT was specified, either use the SET CONNECTION
statement to make relational database &1 the current connection or change
the RDB directory entry (CHGRDBDIRE) for the relational database you are
connecting to so that at least part of the communication information is
different from what is specified in the entry for &1. For APPC connections,
the communication information is the remote location, device description,
local location, remote network identifier, mode, and transaction program.
For TCP/IP connections, the communication information is the remote location
and port identification.
This suggests that there's another active SQL connection to the database. Because CPYFRMIMPF uses SQL behind the scenes, I can see why it would need an SQL connection, but in my experience, the operating system manages this automatically. Are you connecting to the system from an outside source, such as running the CL from a client application via a RMTCMD or something?