\begin{frame}
  \frametitle{Example}

  \begin{quiz}{\textwidth}{}
    \begin{tcenter}
      {\small\def\scheduleWidth{1cm}
      \begin{tikzpicture}
        \schedule{}{3}{1rV|2rY|3wV|1rZ|2wV|1rY|3wZ}
      \end{tikzpicture}
      }
    \end{tcenter}

    \begin{itemize}
      \item Can it be achieved using 2 PL?\\
      \item Can it be achieved using Strict 2 PL?
    \end{itemize}
    Add the corresponding lock and unlock statements.
    \medskip\pause
    
    \hspace*{-.2cm}%
    \scalebox{.85}{
    {\footnotesize\def\scheduleWidth{.68cm}\def\scheduleOffset{.5cm}
    \begin{tikzpicture}
      \only<-2>{ \schedule{}{3}{1sV|1rV|2sY|2rY|3xV|3wV|1sZ|1rZ|2xV|2wV|1sY|1rY|3xZ|3wZ} }
      \only<3-4>{ \schedule{}{3}{1SV|1rV|2sY|2rY|3XV|3wV|1sZ|1rZ|2xV|2wV|1sY|1rY|3xZ|3wZ} }
      \only<5>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|2xV|2wV|1rY|3xZ|3wZ} }
      \only<5->{ \node at (2*\scheduleWidth - .2cm,-.5*\scheduleHeight) {\tshared{V\alert<10>{Z}Y}}; }
      \only<6>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3XV|3wV|1rZ|2XV|2wV|1rY|3xZ|3wZ} }
      \only<7>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|3uV|2xV|2wV|1rY|3xZ|3wZ} }
      \only<8>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|3UV|2xV|2wV|1rY|3XZ|3wZ} }
      \only<9>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|3xZ|3uV|2xV|2wV|1rY|3wZ} }
      \only<10>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|3XZ|3uV|2xV|2wV|1rY|3wZ} }
      \only<11>{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|1uZ|3xZ|3uV|2xV|2wV|1rY|3wZ} }
      \only<12->{ \schedule{}{3}{1_ |1_ |1rV|1uV|2sY|2rY|3xV|3wV|1rZ|1uZ|3xZ|3uV|2xV|2wV|1rY|3wZ|1uY|1_ } }
      \only<12->{ 
        \node at (18*\scheduleWidth,-1.5*\scheduleHeight) {\tunlock{VY}}; 
        \node at (18*\scheduleWidth,-2.5*\scheduleHeight) {\tunlock{Z}}; 
      }
    \end{tikzpicture}
    }}%
    \medskip

    \onslide<4->{\alert{Impossible with Strict 2 PL: $T_1$ must hold lock on $V$ until commit.}}%
    \pause[13]%
    \smallskip
    
    This schedule is 2 PL !
    \smallskip\pause
    
    Can it be achieved using Preclaiming 2 PL? \pause No
  \end{quiz}  
\end{frame}