Undo Logging
Example
Initial state: A = 10, B = 50.
| step |
action |
log record |
| 1 |
|
begin(T1) |
| 2 |
read(A, v) |
|
| 3 |
v = v * 2 |
|
| 4 |
write(A, v) |
update(T1, A, 10) |
| 5 |
read(B, v) |
|
| 6 |
v = v + 1 |
|
| 7 |
write(B, v) |
update(T1, B, 50) |
| 8 |
flush() |
|
| 9 |
output(A) |
|
| 10 |
output(B) |
|
| 11 |
|
commit(T1) |
| 12 |
flush() |
|
|
|
|