Disk Operations and Log Records

Question $1(5$ points$)$

Assume that initially A$=5$ and B$=10$ are values on hard disk. The following is a

transaction T$1$ of user program on A and B $(->$ denotes assignment, $\text{'}$;$\text{'}$ gives order of

operations$)$:

T$1$:A$+$B$"->$ A; A$+$B $->$ B $"$

T$1$ generates the following actions $($read$/$write$/$output$)$ to the database:

T$1$: Read$($A$,$ t$)$; Read$($B$,$ u$)$; t$+$u $->$ t; Write$($A$,$ t$)$; t$+$u $->$ u; Write$($B$,$ u$)$; Output$($A$)$;

Output$($B$)$;

and the following undo$/$redo log records:

; ; ;

For the following transaction T$2,$

T$2$: A$+$B $->$ B; A$+$B $->$ A

$1.$Add necessary read$/$write$/$output actions to the computation;

$2.$ Show the undo$/$redo log records it generates.