16401, 00000, "archivelog rejected by RFS"
// *Cause: An attempt was made to re-archive an existing archivelog.
// This usually happens because either a multiple primary database or
// standby database(s) or both are trying to archive to
// this standby database.
// *Action: See alert log and trace file for more details.
// No action is necessary; this is an informational statement provided
// to record the event for diagnostic purposes.
No need to describe this more..as it's just an information message.