When you ever get this error
Then go to adf-config.xml and then remove the mdsC:adf-mds-config entry completely.
The content of the tag goes like this
<mdsC:adf-mds-config version="11.1.1.000"> <mds-config xmlns="http://xmlns.oracle.com/mds/config"> <persistence-config> <metadata-namespaces> persdef/" metadata-store-usage="WebCenterFileMetadataStore"/> </metadata-namespaces> <metadata-store-usages> <metadata-store-usage id="WebCenterFileMetadataStore" default-cust-store="true" deploy-target="true"> <metadata-store class-name="oracle.mds.dt.persistence.stores.file.SrcControlFileMetadataStore"> <property name="metadata-path" value="../../mds"/> </metadata-store> </metadata-store-usage> </metadata-store-usages> </persistence-config> <cust-config> <match> <customization-class name="oracle.adf.share.config.SiteCC"/> </match> </cust-config> <cache-config> <max-size-kb>100000</max-size-kb> </cache-config> </mds-config> <!--<span class="hiddenSpellError" pre=""-->mdsC:adf-mds-config>