Communication between the Loader and the database instance takes place via the synchronous exchange of communication packages. The Loader sends a package containing the command that is to be processed to the database instance. This is known as a "request". While the database instance processes the command, the Loader waits for the package to be returned with the result. This is known as a "receive".
Errors may occur during this process if the connection from the Loader to the database instance is lost or if the database instance is no longer available.
Use the error text to determine why the communication failed. Fix the cause or the error and restart the Loader.