\begin{frame}
  \frametitle{Cascading Rollbacks}
  
  \begin{quiz}{\textwidth}{What is the problem here?}
  \begin{center}
    {\def\scheduleWidth{.8cm}\small
    \begin{tikzpicture}
      \schedule{}{2}{1xA|1sB|1wA!1+2|1uA|2sA|2rA!1+2|2xA|2wA|2uA|1rB|1uB}
    \end{tikzpicture}
    }
  \end{center}
  Assume that:
  \begin{itemize}
    \item $T_1$ is aborted (due to a conflict with another transaction)
    \item $T_2$ tries to commit 
  \end{itemize}
  \medskip

  What is the problem here?
  \pause
  \begin{itemize}
    \item $T_2$ has read a value written by $T_1$.
  \pause
    \item Thus if $T_1$ is aborted, then \alert{$T_2$ needs to be aborted too}. \\
      \remark{The commit will result in an abort.}
  \end{itemize}
  \end{quiz}
\end{frame}