16635, 0000, "network connection failed during transmission"
*Cause: The Data Guard broker detected a connection failure to a remote
database in the broker configuration. This failure happened
in the middle of a transmission session. A transmission session
usually requires more than one send operation for sending a large
amount of data (for example, the broker configuration file) to
the remote database.
*Action: In most cases, no user action is required. The Data Guard broker
always tries to resend the data. This error will be reported if the
problem persists. This error indicates there are some problems
with the network connection between broker managed databases.
Further network troubleshooting should be done to identify and
correct the actual problem.