The main storage units required for redo log management are the log pages. The size of the log pages is 8 KB.
·
A transaction writes
redo log
entries to the log pages of the log
queues.
Each log page is assigned a log queue sequence number, which specifies the time at which the redo log entries are written to the log queue.
·
If a log page is to be
written to the log area, the log writer is
notified. The log writer fetches
the log pages in question from the log queue, and writes them to the log
area.
When each log page is written from the log queue to the log area, the log writer assigns it a log sequence number and a time stamp. These log sequence numbers can then be used to determine the unique sequence of the log pages in the log area. The time stamp is needed for a point-in-time recovery.
A log page that was written by the log writer, but was not full, remains in the log queue and can be filled with further redo log entries.