Database Reference
In-Depth Information
Block Buffer
Cache
Redo Log
Buffer
Table T
Undo
Indexes
Redo
Figure 9-2.
State of the system after a redo log buffer flush
That is, we'll have modified blocks representing uncommitted changes in the buffer cache and redo for those
uncommitted changes on disk. This is a very normal scenario that happens frequently.
The UPDATE
The
UPDATE
will cause much of the same work as the
INSERT
to take place. This time, the amount of undo will be
larger; we have some “before” images to save as a result of the
UPDATE
. Now we have the picture shown in Figure
9-3
(the dark rectangle in the redo log file represents the redo generated by the
INSERT
, the redo for the
UPDATE
is still in
the SGA and has not yet been written to disk).
Block Buffer
Cache
Redo Log
Buffer
Redo
Undo
Indexes
Table T
Figure 9-3.
State of the system after the
UPDATE
