Oracle Message PGA-21046 - logging switched to system log due to error on log file

ERRORlogging switched to system log due to error on log file
CAUSEAn error occurred writing to the log file, and logging as been switched to the system log facility for the remainder of this RRM execution.
ACTIONCorrect the problem that cause d the error on the log file, so that the next restart of the RRM will be able to write to the log file. A common cause for this message is unavailable disk space for the file.