When do LGWR writes the data into the online redo log files ?

1.If one third of the redo buffer cache is filled.

2.If the data reaches 1MB.

3.if the user commits.

4.For every 3 seconds.

5.Before DBWR writes the data to the respective data file.

 

Every online redo log file will have a log sequence number and this number gets incremented automatically during the operations of the database.

 

Whenever, log switch occurs, checkpoint occurs which will be caused by the CKPT background process.

During checkpoint, CKPT signals DBWR background process to write thedirty buffers to the respective data files.

Whenever checkpoint occurs, CKPT updates the checkpoint change number to the control files as well as the data file headers.