OCI-60508
invalid refresh SCN string specified. Max possible refresh SCN string
Cause
An attempt was made to refresh the pluggable database to a system change number (SCN) that was greater than the source Container Database's (CDB) current SCN or the maximum SCN of the archive logs available in the refresh catalog or in the remote_recovery_file_dest
Action
Reissue the statement with a valid SCN number or refresh without the UNTIL SCN clause.