\showframe

\definelayout
  [test]
  [width=12cm,
   height=10cm]

\definelayout
  [more]
  [test]
  [height=12cm]

\starttext

    \setuplayout         \subject{normal} \input ward \page
    \setuplayout [test]  \subject{test}   \input ward \page
    \setuplayout         \subject{normal} \input ward \page
    \setuplayout [test]  \subject{test}   \input ward \page
    \setuplayout [more]  \subject{more}   \input ward \page
    \setuplayout [test]  \subject{test}   \input ward \page
    \setuplayout [reset] \subject{reset}  \input ward \page

\stoptext

