@Override
  public void unlockRegionForAtomicTX(InternalRegion r) {
    if (armLockTestHook != null) {
      armLockTestHook.beforeRelease(r, null);
    }

    RegionVersionVector vector = r.getVersionVector();
    if (vector != null) {
      vector.releaseCacheModificationLock();
    }

    if (armLockTestHook != null) {
      armLockTestHook.afterRelease(r, null);
    }
  }
release version-generation permission from the region's version vector
geode-core/src/main/java/org/apache/geode/internal/cache/AbstractRegionMap.java