/**
  * Set a random DiskStore for the region defined with regionConfigName if it is persistent or has
  * eviction with overflow to disk.
  *
  * @param regionConfigName A hydra region config name. return factory The attributes factory for
  *     the regionConfigName with possibly a DiskStore.
  */
 public static AttributesFactory setDiskStoreIfNeeded(String regionConfigName) {
   AttributesFactory factory = RegionHelper.getAttributesFactory(regionConfigName);
   RegionDescription desc = RegionHelper.getRegionDescription(regionConfigName);
   EvictionAttributes evAttr = desc.getEvictionAttributes();
   if ((desc.getDataPolicy().withPersistence())
       || ((evAttr != null) && (evAttr.getAction().isOverflowToDisk()))) {
     List diskStoreNames = TestConfig.tab().vecAt(DiskStorePrms.names);
     factory.setDiskStoreName(
         (String)
             (diskStoreNames.get(
                 TestConfig.tab().getRandGen().nextInt(1, diskStoreNames.size() - 1))));
   }
   return factory;
 }