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>