Clustering is not currently supported for the Document Viewer Agent (DVA).
However, clustering is not necessary in order to provide high availability for the DVA, because the DVA does not require the database access that is required by the MTA and POA. As an alternative to clustering the DVA, you can install the DVA on multiple servers outside the cluster, as described in
Scaling Your DVA Installation in
Document Viewer Agent in the GroupWise 2012 Administration Guide.