diff --git a/CMakeLists.txt b/CMakeLists.txt
index 60a90db7..e2295637 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,7 +17,7 @@ endif()
 # Metall general configuration
 # -------------------------------------------------------------------------------- #
 project(Metall
-        VERSION 0.23.1
+        VERSION 0.24
         DESCRIPTION "A persistent memory allocator for data-centric analytics"
         HOMEPAGE_URL "https://github.com/LLNL/metall")
 
diff --git a/bench/data_structure/multithread_adjacency_list.hpp b/bench/data_structure/multithread_adjacency_list.hpp
index 876bf92e..eed559fd 100644
--- a/bench/data_structure/multithread_adjacency_list.hpp
+++ b/bench/data_structure/multithread_adjacency_list.hpp
@@ -193,9 +193,9 @@ class multithread_adjacency_list<_key_type, _value_type, _base_allocator_type>::
     return !(*this == other);
   }
 
-  reference operator++() {
+  impl_const_key_iterator& operator++() {
     next();
-    return *m_local_iterator;
+    return *this;
   }
 
   impl_const_key_iterator operator++(int) {
diff --git a/bench/data_structure/partitioned_multithread_adjacency_list.hpp b/bench/data_structure/partitioned_multithread_adjacency_list.hpp
index c0b16fc1..091c9016 100644
--- a/bench/data_structure/partitioned_multithread_adjacency_list.hpp
+++ b/bench/data_structure/partitioned_multithread_adjacency_list.hpp
@@ -174,9 +174,9 @@ class partitioned_multithread_adjacency_list<local_adj_list_type, global_allocat
     return !(*this == other);
   }
 
-  reference operator++() {
+  impl_key_iterator& operator++() {
     next();
-    return *m_local_iterator;
+    return *this;
   }
 
   impl_key_iterator operator++(int) {
diff --git a/docs/Doxyfile.in b/docs/Doxyfile.in
index eebd3653..389327da 100644
--- a/docs/Doxyfile.in
+++ b/docs/Doxyfile.in
@@ -38,7 +38,7 @@ PROJECT_NAME           = "Metall"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = v0.23.1
+PROJECT_NUMBER         = v0.24
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/include/metall/container/experimental/json/value.hpp b/include/metall/container/experimental/json/value.hpp
index 32b249f1..642814bb 100644
--- a/include/metall/container/experimental/json/value.hpp
+++ b/include/metall/container/experimental/json/value.hpp
@@ -142,7 +142,20 @@ class value {
                                  std::true_type>) {
       m_allocator = other.m_allocator;
     }
-    m_data = other.m_data;
+
+    // Cannot do `m_data = other.m_data`
+    // because std::variant calls the allocator-extended copy constructor of the holding data,
+    // which ignores propagate_on_container_copy_assignment value.
+    if (other.is_object()) {
+      emplace_object() = other.as_object();
+    } else if (other.is_array()) {
+      emplace_array() = other.as_array();
+    } else if (other.is_string()) {
+      emplace_string() = other.as_string();
+    } else {
+      m_data = other.m_data;
+    }
+
     return *this;
   }
 
diff --git a/include/metall/kernel/manager_kernel_impl.ipp b/include/metall/kernel/manager_kernel_impl.ipp
index f8d0957c..b5d28ec6 100644
--- a/include/metall/kernel/manager_kernel_impl.ipp
+++ b/include/metall/kernel/manager_kernel_impl.ipp
@@ -1173,6 +1173,13 @@ bool manager_kernel<chnk_no, chnk_sz>::priv_copy_data_store(const std::string &s
                                                             const std::string &dst_base_dir_path,
                                                             const bool use_clone,
                                                             const int num_max_copy_threads) {
+  if (!consistent(src_base_dir_path.data())) {
+    std::string s(
+        "Source directory is not consistnt (may not have closed properly or may still be open): " + src_base_dir_path);
+    logger::out(logger::level::error, __FILE__, __LINE__, s.c_str());
+    return false;
+  }
+
   const std::string src_top_dir = priv_make_top_dir_path(src_base_dir_path);
   if (!mdtl::directory_exist(src_top_dir)) {
     std::string s("Source directory does not exist: " + src_top_dir);
diff --git a/include/metall/stl_allocator.hpp b/include/metall/stl_allocator.hpp
index 20f2fcf8..c6b2db40 100644
--- a/include/metall/stl_allocator.hpp
+++ b/include/metall/stl_allocator.hpp
@@ -17,9 +17,17 @@
 
 namespace metall {
 
-/// \brief A STL compatible allocator
-/// \tparam T The type of the object
-/// \tparam metall_manager_kernel_type The type of the manager kernel
+/// \brief A STL compatible allocator.
+/// \tparam T A object type.
+/// \tparam metall_manager_kernel_type A manager kernel type.
+/// \warning
+/// This allocator does not define propagate_on_* types, as same as Boost.Interprocess.
+/// Those types are going to be std::false_type in std::allocator_traits.
+/// Therefore, this allocator is not propagated during containers' copy assignment, move assignment, or swap.
+/// This configuration enables users to copy containers between different Metall managers easier.
+/// On the other hand, performing the move assignment between two containers allocated by different Metall managers
+/// invokes copy operations instead of move operations.
+/// Also, swapping containers allocated by different Metall managers will result in undefined behavior.
 template <typename T, typename metall_manager_kernel_type>
 class stl_allocator {
 
@@ -35,10 +43,6 @@ class stl_allocator {
   using const_void_pointer = typename std::pointer_traits<pointer>::template rebind<const void>;
   using difference_type = typename std::pointer_traits<pointer>::difference_type;
   using size_type = typename std::make_unsigned<difference_type>::type;
-  using propagate_on_container_copy_assignment = std::true_type;
-  using propagate_on_container_move_assignment = std::true_type;
-  using propagate_on_container_swap = std::true_type;
-  using is_always_equal = std::false_type;
   using manager_kernel_type = metall_manager_kernel_type;
 
   /// \brief Makes another allocator type for type T2
@@ -133,12 +137,6 @@ class stl_allocator {
   void destroy(const pointer &ptr) const {
     priv_destroy(ptr);
   }
-  /// \brief Obtains the copy-constructed version of the allocator a.
-  /// \param a Allocator used by a standard container passed as an argument to a container copy constructor.
-  /// \return The allocator to use by the copy-constructed standard containers.
-  stl_allocator select_on_container_copy_construction(const stl_allocator &a) {
-    return stl_allocator(a);
-  }
 
   // ----------------------------------- This class's unique public functions ----------------------------------- //
   /// \brief Returns a pointer that points to manager kernel
diff --git a/include/metall/utility/metall_mpi_adaptor.hpp b/include/metall/utility/metall_mpi_adaptor.hpp
index a090ead3..6b84b63c 100644
--- a/include/metall/utility/metall_mpi_adaptor.hpp
+++ b/include/metall/utility/metall_mpi_adaptor.hpp
@@ -135,6 +135,7 @@ class metall_mpi_adaptor {
   }
 
   /// \brief Copies a Metall datastore to another location.
+  /// The behavior of copying a data store that is open without the read-only mode is undefined.
   /// \param source_dir_path A path to a source datastore.
   /// \param destination_dir_path A path to a destination datastore.
   /// \param comm A MPI communicator.
@@ -143,6 +144,15 @@ class metall_mpi_adaptor {
   static bool copy(const char *source_dir_path,
                    const char *destination_dir_path,
                    const MPI_Comm &comm = MPI_COMM_WORLD) {
+    if (!consistent(source_dir_path, comm)) {
+      if (priv_mpi_comm_rank(comm) == 0) {
+        std::stringstream ss;
+        ss << "Source directory is not consistnt (may not have closed properly or may still be open): "
+           << source_dir_path;
+        logger::out(logger::level::error, __FILE__, __LINE__, ss.str().c_str());
+      }
+      return false;
+    }
     priv_setup_root_dir(destination_dir_path, comm);
     const int rank = priv_mpi_comm_rank(comm);
     return priv_global_and(manager_type::copy(ds::make_local_dir_path(source_dir_path, rank).c_str(),
diff --git a/include/metall/version.hpp b/include/metall/version.hpp
index 90bb19cd..66710a28 100644
--- a/include/metall/version.hpp
+++ b/include/metall/version.hpp
@@ -14,7 +14,7 @@
 ///  METALL_VERSION / 100 % 1000 // the minor version.
 ///  METALL_VERSION % 100 // the patch level.
 /// \endcode
-#define METALL_VERSION 2301
+#define METALL_VERSION 2400
 
 namespace metall {
 /// \brief Variable type to handle a version data.
diff --git a/test/container/stl_allocator_test.cpp b/test/container/stl_allocator_test.cpp
index 7e4aaf76..320e7344 100644
--- a/test/container/stl_allocator_test.cpp
+++ b/test/container/stl_allocator_test.cpp
@@ -51,21 +51,21 @@ TEST(StlAllocatorTest, Types) {
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::size_type), typeid(alloc_t::size_type));
 
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_copy_assignment),
-                    typeid(alloc_t::propagate_on_container_copy_assignment));
+                    typeid(std::false_type));
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_copy_assignment),
-                    typeid(std::true_type));
+                    typeid(std::false_type));
 
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_move_assignment),
-                    typeid(alloc_t::propagate_on_container_move_assignment));
+                    typeid(std::false_type));
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_move_assignment),
-                    typeid(std::true_type));
+                    typeid(std::false_type));
 
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_swap),
-                    typeid(alloc_t::propagate_on_container_swap));
-    GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_swap), typeid(std::true_type));
+                    typeid(std::false_type));
+    GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::propagate_on_container_swap), typeid(std::false_type));
 
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::is_always_equal),
-                    typeid(alloc_t::is_always_equal));
+                    typeid(std::false_type));
     GTEST_ASSERT_EQ(typeid(std::allocator_traits<alloc_t>::is_always_equal), typeid(std::false_type));
 
     using otherT = int;