The productCatalogSearch page determines the correct content URI using the contentURI parameter. If the contentURI is not found, the page looks at the cached content URI from the SearchState, which is a session-scoped component that holds data on the most recently requested content URI. If the contentURI is still not found, the page uses the defaultcontentURI value that has been entered in the configuration.properties file. It then updates the cache contentURI in the SearchState:

<c:if test="${empty endecaContentURI}">
  <c:set var="endecaContentURI" value="${searchState.lastContentURI}"/>
  <c:if test="${empty endecaContentURI}">
    <c:set var="endecaContentURI"
        value="${endecaConfig.defaultContentURI}"/>
  </c:if>
</c:if>
<dsp:setvalue bean="/atg/commerce/custsvc/catalog/
    endeca/SearchState.lastContentURI" value="${endecaContentURI}"/>