public void offlineCompact() {
    if (getChild() != null) {
      // check active oplog and if it is empty delete it
      getChild().krfClose();
      if (getChild().isOplogEmpty()) {
        getChild().destroy();
      }
    }

    // remove any oplogs that only have a drf
    Collection<Oplog> oplogsToDestroy = new ArrayList<>();
    synchronized (getOplogIdToOplog()) {
      for (Oplog oplog : getOplogIdToOplog().values()) {
        if (oplog.isDrfOnly()) {
          oplogsToDestroy.add(oplog);
        }
      }
    }

    for (Oplog oplog : oplogsToDestroy) {
      oplog.destroy();
    }

    destroyOldestReadyToCompact();
  }
Returns null if we are not currently recovering the DiskRegion with the given drId.
geode-core/src/main/java/org/apache/geode/internal/cache/PersistentOplogSet.java