Know more about redo log buffer and latches

1.

The Total size of the log buffer is determined by LOG_BUFFER parameter.

2.

Only Server process may pin a data block in exclusive mode.

3.

LGWR writes to the redo log files when:

• The redo log buffer is 1/3 full.
• 1 MB of data have been written to the redo log buffer.
• A 3-second time-out occurs.
• commit!
• before dbwr write out dirty buffers
• A thread is closed

4.

the correct sequence for the LGWR algorithm is :

1. Acquire the redo writing and redo allocation latches
2. determine the buffer to write out
3. Release the redo allocation latch
4. determine how many writes are required

5.

In Oracle8i, the redo copy latch is always acquired regardless of the redo size.

Because the parameter LOG_SMALL_ENTRY_MAX_SIZE is obsolete, a redo copy latch is always acquired.

6.

Three most relevant redo events under normal operations:

• Log file parallel write
• Log buffer space
• Log file sync

7.

relevant redo statistics and their purpose

• REDO writes