The second redo log file is transferred to the archive log by ARCN procecess. The switch operation is repeated and the third redo log file starts to be used. Let’s think the second redo log file is full. The ARCn process copies the full redo log file to the archive log file. When the first redo log file is written, the log switch operation is performed and the redo log file is passed to the second redo log file.Īs the first redo log file is full, it starts archiving. I am going to go through an example to make it clearer.įor example, we assume that the database is in archive log mode. I would like to point out that this information is useful for our work in the later stages of the article. In this sense RAC also offers us the performance advantage.Įach redo and archive log file has a unique log sequence number. If you are using the RAC architecture, each node has separate redo log files for the database. If you create multiple redo log files in an Oracle Single Instance, you always write to one redo log file.

You must change the size of the redo log file and the number of redo log files in the default installation according to your system needs. One is required for the current use and the other for the archive log.

If the database is in archivelog mode, there should be at least 2 redo log files for each database. It is then written to the active Redo Log used by LGWR. Oracle uses Redo Logs and Archive Logs to ensure that the data written to the database will not be lost once it has been written and can be recovered to the desired moment.Įach modification operation (Update, Insert, Delete, Alter, etc.) made in the database is first written to the Redo Log Buffer.

Oracle database log