code: public static synchronized void truncateStorage(final StorageConfiguration pConf) throws TTException {
          // check that database must be closed beforehand
          if (!STORAGEMAP.containsKey(pConf.mFile)) {
              if (existsStorage(pConf.mFile)) {
                  final IStorage storage = new Storage(pConf);
                  final File[] resources =
                      new File(pConf.mFile, StorageConfiguration.Paths.Data.getFile().getName()).listFiles();
                  for (final File resource : resources) {
                      storage.truncateResource(new SessionConfiguration(resource.getName(), null));
                  }
                  storage.close();
                  // instantiate the database for deletion
                  IOUtils.recursiveDelete(pConf.mFile);
              }
          }
      }
docs: Truncate a storage. This deletes all relevant data. All running sessions
  must be closed beforehand.
  
  @param pConf
  the storage at this path should be deleted.
  @throws TTException
  any kind of false Treetank behaviour