The default implementation for the Provenance Repository is the PersistentProvenanceRepository. The WriteAheadProvenanceRepository was added in version 1.2.0 of NiFi. We left the default as the PersistentProvenanceRepository only because it had been heavily tested over years of production use. Since then, the WriteAheadProvenanceRepository has proven to be not only significantly faster but also more stable and easier to maintain. When problems arise with the PersistentProvenanceRepository, the solution almost always is to change to the WriteAheadProvenanceRepository. Given this, we should now change the default implementation to be the WriteAheadProvenanceRepository.
This involves changing the default value in the POM of nifi-resources and also updating the Admin Guide to note the new default and review the guide for any other wording that may need to be updated.