When a redo log file fills up it switches to the next file. This is called a log switch.
The log switch always causes a checkpoint to occur. This flushes all dirty buffers from the log cache. (writes modified data to disk)
If archiving is on, the old log file id archived.
The new log file is given a log sequence number which is also given to the archived log file.
Controlint the checkpoint
LOG_CHECKPOINT_INTERVAL
set to the number of operating system blocks that can be used before a checkpoint occurs.
LOG_CHECKPOINTS_TO_ALERT
Writes a message to the alert log when a checkpoint occurs.
This can take up a lot of space!
LOG_CHECKPOINT_TIMEOUT
Set the time in seconds bertween checkpoints
Force a checkpoint
ALTER SYSTEM CHECKPOINT
You may do this if there is a risk of the system failing.
Force a log switch
ALTER SYSTEM SWITCH LOGFILE;
you will rarely need to do this.
