Primefaces DataTable auto/dynamic height example

Defina os valores height: calc(100vh - 270px) de acordo com seu layout.

<p:dataTable scrollable="true"
 crollHeight="display: flex;overflow: auto;height: calc(100vh - 270px);position: relative;">

Ou

.divDataTablePrincipal {
    display: flex!important;
    overflow: auto!important;
    height: calc(100vh - 240px)!important;
    position: relative!important;
}

<div class="divDataTablePrincipal">
  <p:dataTable>

  </p:dataTable>
</div>