public static boolean isCRFFile(String filename) {
    return filename.endsWith(Oplog.CRF_FILE_EXT);
  }
Copy any live entries last stored in this oplog to the current oplog. No need to copy deletes
in the drf. Backup only needs them until all the older crfs are empty.
geode-core/src/main/java/org/apache/geode/internal/cache/Oplog.java