private void doPuts(String regionName, int from, int count) {
    Region<Number, String> region = getCache().getRegion(SEPARATOR + regionName);
    for (int i = from; i < count; i++) {
      region.put(i, "Value_" + i);
    }
  }
Since the sender is attached to a region and in use, it can not be destroyed. Hence, exception
is thrown by the sender API.
geode-wan/src/distributedTest/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderOperationsDistributedTest.java