Consider the following two transactions:

T$1=$ R$($A$)$ W$($A$)$ R$($B$)$ W$($B$)$

T$2=$ R$($B$)$ R$($A$)$ W$($A$)$ W$($B$)$

Assume that exclusive lock $($X$)$ and unlock $($U$)$ actions are inserted by the scheduler, resulting

in the following annotated transactions:

T$1=$ X$($A$)$ R$($A$)$ W$($A$)$ X$($B$)$ R$($B$)$ W$($B$),$ AFTER COMMIT: U$($A$)$ U$($B$)$

T$2=$ X$($B$)$ R$($B$)$ X$($A$)$ R$($A$)$ W$($A$)$ W$($B$),$ AFTER COMMIT: U$($A$)$ U$($B