diff --git a/CMakeLists.txt b/CMakeLists.txt
index 78e1fbd..672b7b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,7 @@ find_package(Boost 1.54.0 REQUIRED
   unit_test_framework
   program_options
   filesystem
+  thread
   )
 
 # Coverage
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 3af900b..a9dbcdc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -27,5 +27,5 @@ add_test(NAME trrep_test
 
 add_executable(dbms_simulator
   dbms_simulator.cpp)
-target_link_libraries(dbms_simulator trrep ${Boost_PROGRAM_OPTIONS_LIBRARY} ${Boost_SYSTEM_LIBRARY} ${Boost_FILESYSTEM_LIBRARY})
+target_link_libraries(dbms_simulator trrep ${Boost_PROGRAM_OPTIONS_LIBRARY} ${Boost_SYSTEM_LIBRARY} ${Boost_FILESYSTEM_LIBRARY} ${Boost_THREAD_LIBRARY})
 set_property(TARGET dbms_simulator PROPERTY CXX_STANDARD 14)
diff --git a/src/client_context.cpp b/src/client_context.cpp
index 5581249..ef6e258 100644
--- a/src/client_context.cpp
+++ b/src/client_context.cpp
@@ -4,6 +4,11 @@
 
 #include "client_context.hpp"
 #include "transaction_context.hpp"
+#include "compiler.hpp"
+
+#include <sstream>
+#include <iostream>
+
 
 trrep::provider& trrep::client_context::provider() const
 {
@@ -12,6 +17,7 @@ trrep::provider& trrep::client_context::provider() const
 
 int trrep::client_context::before_command()
 {
+    trrep::unique_lock<trrep::mutex> lock(mutex_);
     assert(state_ == s_idle);
     if (server_context_.rollback_mode() == trrep::server_context::rm_sync)
     {
@@ -26,7 +32,7 @@ int trrep::client_context::before_command()
             // cond_.wait(lock);
         }
     }
-    state_ = s_exec;
+    state(lock, s_exec);
     if (transaction_.state() == trrep::transaction_context::s_must_abort)
     {
         return 1;
@@ -45,7 +51,7 @@ int trrep::client_context::after_command()
         lock.lock();
         ret = 1;
     }
-    state_ = s_idle;
+    state(lock, s_idle);
     return ret;
 }
 
@@ -72,5 +78,33 @@ int trrep::client_context::after_statement()
      * \todo Check for replay state, do rollback if requested.
      */
 #endif // 0
+    transaction_.after_statement();
     return 0;
 }
+
+// Private
+
+void trrep::client_context::state(
+    trrep::unique_lock<trrep::mutex>& lock TRREP_UNUSED,
+    enum trrep::client_context::state state)
+{
+    assert(lock.owns_lock());
+    char allowed[state_max_][state_max_] =
+        {
+            /* idle exec quit */
+            {  0,   1,   1}, /* idle */
+            {  1,   0,   1}, /* exec */
+            {  0,   0,   0}
+        };
+    if (allowed[state_][state])
+    {
+        state_ = state;
+    }
+    else
+    {
+        std::ostringstream os;
+        os << "client_context: Unallowed state transition: "
+           << state_ << " -> " << state << "\n";
+        throw trrep::runtime_error(os.str());
+    }
+}
diff --git a/src/client_context.hpp b/src/client_context.hpp
index 821ab57..3f0c6d3 100644
--- a/src/client_context.hpp
+++ b/src/client_context.hpp
@@ -113,10 +113,14 @@ namespace trrep
             s_quitting
         };
 
+        const static int state_max_ = s_quitting + 1;
         /*!
          * Destructor.
          */
-        virtual ~client_context() { }
+        virtual ~client_context()
+        {
+            assert(transaction_.active() == false);
+        }
 
         /*!
          * Virtual method which should be called before the client
@@ -172,6 +176,68 @@ namespace trrep
          */
         virtual int after_statement();
 
+        int start_transaction(const trrep::transaction_id& id)
+        {
+            assert(state_ == s_exec);
+            return transaction_.start_transaction(id);
+        }
+
+        int start_transaction(const wsrep_ws_handle_t& wsh,
+                              const wsrep_trx_meta_t& meta,
+                              uint32_t flags)
+        {
+            assert(mode_ == m_applier);
+            return transaction_.start_transaction(wsh, meta, flags);
+        }
+
+        int append_key(const trrep::key& key)
+        {
+            assert(state_ == s_exec);
+            return transaction_.append_key(key);
+        }
+
+        int append_data(const trrep::data& data)
+        {
+            assert(state_ == s_exec);
+            return transaction_.append_data(data);
+        }
+        int before_prepare()
+        {
+            assert(state_ == s_exec);
+            return transaction_.before_prepare();
+        }
+        int after_prepare()
+        {
+            assert(state_ == s_exec);
+            return transaction_.after_prepare();
+        }
+        int before_commit()
+        {
+            assert(state_ == s_exec);
+            return transaction_.before_commit();
+        }
+
+        int ordered_commit()
+        {
+            assert(state_ == s_exec);
+            return transaction_.ordered_commit();
+        }
+
+        int after_commit()
+        {
+            assert(state_ == s_exec);
+            return transaction_.after_commit();
+        }
+        int before_rollback()
+        {
+            assert(state_ == s_exec);
+            return transaction_.before_rollback();
+        }
+        int after_rollback()
+        {
+            assert(state_ == s_exec);
+            return transaction_.after_rollback();
+        }
         /*!
          * Get reference to the client mutex.
          *
@@ -213,6 +279,10 @@ namespace trrep
          */
         enum mode mode() const { return mode_; }
 
+        trrep::transaction_context& transaction()
+        {
+            return transaction_;
+        }
     protected:
         /*!
          * Client context constuctor. This is protected so that it
@@ -232,6 +302,9 @@ namespace trrep
         { }
 
     private:
+        client_context(const client_context&);
+        client_context& operator=(client_context&);
+
         /*
          * Friend declarations
          */
@@ -250,6 +323,11 @@ namespace trrep
          */
         enum state state() const { return state_; }
 
+        /*!
+         * Set client state.
+         */
+        void state(trrep::unique_lock<trrep::mutex>& lock, enum state state);
+
         /*!
          * Virtual method to return true if the client operates
          * in two phase commit mode.
@@ -324,14 +402,34 @@ namespace trrep
          *
          */
         virtual void override_error(const trrep::client_error&) = 0;
+
+        /*!
+         * Return true if the current client operation was killed.
+         */
         virtual bool killed() const = 0;
+
+        /*!
+         * Abort server operation on fatal error. This should be used
+         * only for critical conditions which would sacrifice data
+         * consistency.
+         */
         virtual void abort() const = 0;
+
+        /*!
+         * Set up thread global variables for client connection.
+         */
         virtual void store_globals() = 0;
-        // Debug helpers
+
+        /*!
+         * Enter debug synchronization point.
+         */
         virtual void debug_sync(const std::string&) = 0;
+
+        /*!
+         *
+         */
         virtual void debug_suicide(const std::string&) = 0;
 
-        void state(enum state state);
 
         trrep::mutex& mutex_;
         trrep::server_context& server_context_;
diff --git a/src/dbms_simulator.cpp b/src/dbms_simulator.cpp
index 3c1ead8..94bad25 100644
--- a/src/dbms_simulator.cpp
+++ b/src/dbms_simulator.cpp
@@ -19,12 +19,14 @@
 
 #include <boost/program_options.hpp>
 #include <boost/filesystem.hpp>
+#include <boost/thread.hpp>
 
 #include <iostream>
 #include <memory>
 #include <map>
 #include <atomic>
-#include <thread>
+#include <chrono>
+// #include <thread>
 
 class dbms_server;
 
@@ -99,12 +101,6 @@ class dbms_client;
 class dbms_server : public trrep::server_context
 {
 public:
-    enum state
-    {
-        s_disconnected,
-        s_connected,
-        s_synced
-    };
     dbms_server(dbms_simulator& simulator,
                 const std::string& name,
                 const std::string& id,
@@ -116,7 +112,6 @@ public:
         , simulator_(simulator)
         , mutex_()
         , cond_()
-        , state_(s_disconnected)
         , last_client_id_(0)
         , last_transaction_id_(0)
         , appliers_()
@@ -131,7 +126,7 @@ public:
     void start_applier()
     {
         trrep::unique_lock<trrep::mutex> lock(mutex_);
-        appliers_.push_back(std::thread(&dbms_server::applier_thread, this));
+        appliers_.push_back(boost::thread(&dbms_server::applier_thread, this));
     }
 
     void stop_applier()
@@ -177,12 +172,11 @@ private:
     dbms_simulator& simulator_;
     trrep::default_mutex mutex_;
     trrep::default_condition_variable cond_;
-    enum state state_;
     std::atomic<size_t> last_client_id_;
     std::atomic<size_t> last_transaction_id_;
-    std::vector<std::thread> appliers_;
+    std::vector<boost::thread> appliers_;
     std::map<size_t, std::unique_ptr<dbms_client>> clients_;
-    std::vector<std::thread> client_threads_;
+    std::vector<boost::thread> client_threads_;
 };
 
 class dbms_client : public trrep::client_context
@@ -196,13 +190,10 @@ public:
         , mutex_()
         , server_(server)
         , n_transactions_(n_transactions)
-        , result_()
     { }
 
-    ~dbms_client()
-    {
-        std::cout << "Result: " << result_;
-    }
+    ~dbms_client() { }
+
     void start()
     {
         for (size_t i(0); i < n_transactions_; ++i)
@@ -257,12 +248,18 @@ private:
 
     void run_one_transaction()
     {
-        trrep::transaction_context trx(*this);
-        trx.start_transaction(server_.next_transaction_id());
-        std::ostringstream os;
+        before_command();
+        before_statement();
+        start_transaction(server_.next_transaction_id());
+        after_statement();
+        after_command();
+
         int err(0);
         for (int i(0); i < 1 && err == 0; ++i)
         {
+            std::ostringstream os;
+            before_command();
+            before_statement();
             int data(std::rand() % 10000000);
             os << data;
             trrep::key key;
@@ -270,24 +267,30 @@ private:
             wsrep_conn_id_t client_id(id().get());
             key.append_key_part(&client_id, sizeof(client_id));
             key.append_key_part(&data, sizeof(data));
-            err = trx.append_key(key);
-            err = err || trx.append_data(trrep::data(os.str().c_str(), os.str().size()));
+            err = append_key(key);
+            err = err || append_data(trrep::data(os.str().c_str(), os.str().size()));
+            after_statement();
+            after_command();
         }
+
+        before_command();
+        before_statement();
         // std::cout << "append_data: " << err << "\n";
-        if (do_2pc())
+        if (err == 0 && do_2pc())
         {
-            err = err || trx.before_prepare();
+            err = err || before_prepare();
             // std::cout << "before_prepare: " << err << "\n";
-            err = err || trx.after_prepare();
+            err = err || after_prepare();
             // std::cout << "after_prepare: " << err << "\n";
         }
-        err = err || trx.before_commit();
+        err = err || before_commit();
         // std::cout << "before_commit: " << err << "\n";
-        err = err || trx.ordered_commit();
+        err = err || ordered_commit();
         // std::cout << "ordered_commit: " << err << "\n";
-        err = err || trx.after_commit();
+        err = err || after_commit();
         // std::cout << "after_commit: " << err << "\n";
-        trx.after_statement();
+        after_statement();
+        after_command();
     }
 
     void report_progress(size_t i) const
@@ -303,7 +306,6 @@ private:
     trrep::default_mutex mutex_;
     dbms_server& server_;
     const size_t n_transactions_;
-    size_t result_;
 };
 
 
@@ -353,7 +355,7 @@ void dbms_server::start_client(size_t id)
                     trrep::client_context::m_replicating,
                     simulator_.params().n_transactions));
     client_threads_.push_back(
-        std::thread(&dbms_server::client_thread, this, client));
+        boost::thread(&dbms_server::client_thread, this, client));
 }
 
 
diff --git a/src/mock_client_context.hpp b/src/mock_client_context.hpp
index 9339843..385a2ec 100644
--- a/src/mock_client_context.hpp
+++ b/src/mock_client_context.hpp
@@ -25,6 +25,13 @@ namespace trrep
             , do_2pc_(do_2pc)
             , fail_next_applying_()
         { }
+        ~mock_client_context()
+        {
+            if (transaction().active())
+            {
+                (void)rollback(transaction());
+            }
+        }
         int apply(trrep::transaction_context&, const trrep::data&);
         int commit(trrep::transaction_context&);
         int rollback(trrep::transaction_context&);
diff --git a/src/mock_utils.cpp b/src/mock_utils.cpp
index 3f26a08..edc8389 100644
--- a/src/mock_utils.cpp
+++ b/src/mock_utils.cpp
@@ -25,7 +25,7 @@ void trrep_mock::bf_abort_provider(trrep::mock_server_context& sc,
     (void)victim_seqno;
 }
 
-trrep::transaction_context trrep_mock::applying_transaction(
+trrep::transaction_context& trrep_mock::start_applying_transaction(
     trrep::client_context& cc,
     const trrep::transaction_id& id,
     wsrep_seqno_t seqno,
@@ -33,10 +33,14 @@ trrep::transaction_context trrep_mock::applying_transaction(
 {
     wsrep_ws_handle_t ws_handle = { id.get(), 0 };
     wsrep_trx_meta_t meta = {
-            { {1 }, seqno }, /* gtid */
-            { { static_cast<uint8_t>(cc.id().get()) }, id.get(), cc.id().get() }, /* stid */
-            seqno - 1
+        { {1 }, seqno }, /* gtid */
+        { { static_cast<uint8_t>(cc.id().get()) }, id.get(), cc.id().get() }, /* stid */
+        seqno - 1
     };
-    trrep::transaction_context ret(cc, ws_handle, meta, flags);
-    return ret;
+    int ret(cc.start_transaction(ws_handle, meta, flags));
+    if (ret != 0)
+    {
+        throw trrep::runtime_error("failed to start applying transaction");
+    }
+    return cc.transaction();
 }
diff --git a/src/mock_utils.hpp b/src/mock_utils.hpp
index 57e738b..a14286f 100644
--- a/src/mock_utils.hpp
+++ b/src/mock_utils.hpp
@@ -28,7 +28,7 @@ namespace trrep_mock
                            const trrep::transaction_context& tc,
                            wsrep_seqno_t bf_seqno);
 
-    trrep::transaction_context applying_transaction(
+    trrep::transaction_context& start_applying_transaction(
         trrep::client_context& cc,
         const trrep::transaction_id& id,
         wsrep_seqno_t seqno,
diff --git a/src/server_context.cpp b/src/server_context.cpp
index 361a872..d832482 100644
--- a/src/server_context.cpp
+++ b/src/server_context.cpp
@@ -113,12 +113,13 @@ namespace
         assert(client_context->mode() == trrep::client_context::m_applier);
 
         trrep::data data(buf->ptr, buf->len);
-        trrep::transaction_context transaction_context(*client_context,
-                                                       *wsh,
-                                                       *meta,
-                                                       flags);
-        if (client_context->server_context().on_apply(
-                *client_context, transaction_context, data))
+        if (client_context->start_transaction(*wsh, *meta, flags))
+        {
+            ret = WSREP_CB_FAILURE;
+        }
+        if (ret == WSREP_CB_SUCCESS &&
+            client_context->server_context().on_apply(
+                *client_context, client_context->transaction(), data))
         {
             ret = WSREP_CB_FAILURE;
         }
@@ -294,11 +295,13 @@ int trrep::server_context::on_apply(
         assert(0);
     }
 
-    transaction_context.after_statement();
     if (ret)
     {
         client_context.rollback(transaction_context);
     }
+
+    transaction_context.after_statement();
+    assert(transaction_context.active() == false);
     return ret;
 }
 
diff --git a/src/server_context.hpp b/src/server_context.hpp
index d48c3cf..f6db5c4 100644
--- a/src/server_context.hpp
+++ b/src/server_context.hpp
@@ -21,7 +21,11 @@
  * State Snapshot Transfer
  * -----------------------
  *
- * TODO
+ * Depending on SST type (physical or logical), the server storage
+ * engine initialization must be done before or after SST happens.
+ * In case of physical SST method (typically rsync, filesystem snapshot)
+ * the SST happens before the storage engine is initialized, in case
+ * of logical backup typically after the storage engine initialization.
  *
  * Rollback Mode
  * -------------
@@ -52,14 +56,6 @@
  * to be aborted or in case of fully optimistic concurrency control,
  * the conflict is detected at commit.
  *
- * SST
- * ===
- *
- * Depending on SST type (physical or logical), the server storage
- * engine initialization must be done before or after SST happens.
- * In case of physical SST method (typically rsync, filesystem snapshot)
- * the SST happens before the storage engine is initialized, in case
- * of logical backup typically after the storage engine initialization.
  */
 
 #ifndef TRREP_SERVER_CONTEXT_HPP
@@ -135,7 +131,9 @@ namespace trrep
             /*! Server is donating state snapshot transfer */
             s_donor,
             /*! Server has synced with the cluster */
-            s_synced
+            s_synced,
+            /*! Server is disconnecting from group */
+            s_disconnecting
         };
         /*!
          * Rollback Mode enumeration
@@ -252,6 +250,10 @@ namespace trrep
          * Wait until server reaches given state.
          *
          * \todo Waiting for transitional states may not be reliable.
+         *       Should introduce array of waiter counts per state,
+         *       on state change the state changing thread is
+         *       not allowed to proceed until all waiters have
+         *       woken up.
          */
         void wait_until_state(trrep::server_context::state) const;
 
@@ -261,6 +263,7 @@ namespace trrep
          * engine initialization, false otherwise.
          */
         virtual bool sst_before_init() const = 0;
+
         /*!
          * Virtual method which will be called on *joiner* when the provider
          * requests the SST request information. This method should
@@ -329,6 +332,7 @@ namespace trrep
         virtual bool statement_allowed_for_streaming(
             const trrep::client_context& client_context,
             const trrep::transaction_context& transaction_context) const;
+
     protected:
                 /*! Server Context constructor
          *
diff --git a/src/server_context_test.cpp b/src/server_context_test.cpp
index a80ea5d..a29ae9b 100644
--- a/src/server_context_test.cpp
+++ b/src/server_context_test.cpp
@@ -16,8 +16,8 @@ BOOST_AUTO_TEST_CASE(server_context_applying_1pc)
                                   trrep::client_id(1),
                                   trrep::client_context::m_applier,
                                   false);
-    trrep::transaction_context tc(
-        trrep_mock::applying_transaction(
+    trrep::transaction_context& tc(
+        trrep_mock::start_applying_transaction(
             cc, 1, 1,
             WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
     char buf[1] = { 1 };
@@ -34,8 +34,8 @@ BOOST_AUTO_TEST_CASE(server_context_applying_2pc)
                                   trrep::client_id(1),
                                   trrep::client_context::m_applier,
                                   true);
-    trrep::transaction_context tc(
-        trrep_mock::applying_transaction(
+    trrep::transaction_context& tc(
+        trrep_mock::start_applying_transaction(
             cc, 1, 1,
             WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
     char buf[1] = { 1 };
@@ -54,11 +54,12 @@ BOOST_AUTO_TEST_CASE(server_context_applying_1pc_rollback)
                                   trrep::client_context::m_applier,
                                   false);
     cc.fail_next_applying(true);
-    trrep::transaction_context tc(
-        trrep_mock::applying_transaction(
+    trrep::transaction_context& tc(
+        trrep_mock::start_applying_transaction(
             cc, 1, 1,
             WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
     char buf[1] = { 1 };
+
     BOOST_REQUIRE(sc.on_apply(cc, tc, trrep::data(buf, 1)) == 1);
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_aborted);
 }
@@ -74,8 +75,8 @@ BOOST_AUTO_TEST_CASE(server_context_applying_2pc_rollback)
                                   trrep::client_context::m_applier,
                                   true);
     cc.fail_next_applying(true);
-    trrep::transaction_context tc(
-        trrep_mock::applying_transaction(
+    trrep::transaction_context& tc(
+        trrep_mock::start_applying_transaction(
             cc, 1, 1,
             WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
     char buf[1] = { 1 };
diff --git a/src/transaction_context.cpp b/src/transaction_context.cpp
index 099301e..ef22bd5 100644
--- a/src/transaction_context.cpp
+++ b/src/transaction_context.cpp
@@ -7,6 +7,7 @@
 #include "server_context.hpp"
 #include "key.hpp"
 #include "data.hpp"
+#include "compiler.hpp"
 
 #include <iostream> // TODO: replace with proper logging utility
 #include <sstream>
@@ -30,40 +31,9 @@ trrep::transaction_context::transaction_context(
     , rollback_replicated_for_(false)
 { }
 
-trrep::transaction_context::transaction_context(
-    trrep::client_context& client_context,
-    const wsrep_ws_handle_t& ws_handle,
-    const wsrep_trx_meta_t& trx_meta,
-    uint32_t flags)
-    : provider_(client_context.provider())
-    , client_context_(client_context)
-    , id_(transaction_id::invalid())
-    , state_(s_executing)
-    , state_hist_()
-    , ws_handle_(ws_handle)
-    , trx_meta_(trx_meta)
-    , flags_(flags)
-    , pa_unsafe_()
-    , certified_(true)
-    , fragments_()
-    , rollback_replicated_for_(false)
-{ }
-
 
 trrep::transaction_context::~transaction_context()
-{
-    if (active())
-    {
-        try
-        {
-            (void)client_context_.rollback(*this);
-        }
-        catch (...)
-        {
-            // TODO: Log warning
-        }
-    }
-}
+{ }
 
 int trrep::transaction_context::start_transaction(
     const trrep::transaction_id& id)
@@ -86,6 +56,21 @@ int trrep::transaction_context::start_transaction(
     }
 }
 
+int trrep::transaction_context::start_transaction(
+    const wsrep_ws_handle_t& ws_handle,
+    const wsrep_trx_meta_t& trx_meta,
+    uint32_t flags)
+{
+    assert(active() == false);
+    assert(client_context_.mode() == trrep::client_context::m_applier);
+    state_ = s_executing;
+    ws_handle_ = ws_handle;
+    trx_meta_ = trx_meta;
+    flags_ = flags;
+    certified_ = true;
+    return 0;
+}
+
 
 int trrep::transaction_context::append_key(const trrep::key& key)
 {
@@ -104,7 +89,7 @@ int trrep::transaction_context::before_prepare()
     int ret(0);
 
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("before_prepare_enter");
     assert(state() == s_executing || state() == s_must_abort);
 
     if (state() == s_must_abort)
@@ -144,7 +129,7 @@ int trrep::transaction_context::before_prepare()
     }
 
     assert(state() == s_preparing);
-    debug_log_state();
+    debug_log_state("before_prepare_leave");
     return ret;
 }
 
@@ -152,7 +137,7 @@ int trrep::transaction_context::after_prepare()
 {
     int ret(1);
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("after_prepare_enter");
     assert(state() == s_preparing || state() == s_must_abort);
     if (state() == s_must_abort)
     {
@@ -184,7 +169,7 @@ int trrep::transaction_context::after_prepare()
         ret = 0;
         break;
     }
-    debug_log_state();
+    debug_log_state("after_prepare_leave");
     return ret;
 }
 
@@ -193,7 +178,7 @@ int trrep::transaction_context::before_commit()
     int ret(1);
 
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("before_commit_enter");
     assert(state() == s_executing || state() == s_committing ||
            state() == s_must_abort);
 
@@ -264,7 +249,7 @@ int trrep::transaction_context::before_commit()
         }
         break;
     }
-    debug_log_state();
+    debug_log_state("before_commit_leave");
     return ret;
 }
 
@@ -273,14 +258,14 @@ int trrep::transaction_context::ordered_commit()
     int ret(1);
 
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("ordered_commit_enter");
     assert(state() == s_committing);
     assert(ordered());
     ret = provider_.commit_order_leave(&ws_handle_, &trx_meta_);
     // Should always succeed
     assert(ret == 0);
     state(lock, s_ordered_commit);
-    debug_log_state();
+    debug_log_state("ordered_commit_leave");
     return ret;
 }
 
@@ -289,7 +274,7 @@ int trrep::transaction_context::after_commit()
     int ret(0);
 
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("after_commit_enter");
     assert(state() == s_ordered_commit);
 
     switch (client_context_.mode())
@@ -309,14 +294,14 @@ int trrep::transaction_context::after_commit()
     }
     assert(ret == 0);
     state(lock, s_committed);
-    debug_log_state();
+    debug_log_state("after_commit_leave");
     return ret;
 }
 
 int trrep::transaction_context::before_rollback()
 {
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("before_rollback_enter");
     assert(state() == s_executing ||
            state() == s_must_abort ||
            state() == s_cert_failed ||
@@ -362,14 +347,14 @@ int trrep::transaction_context::before_rollback()
         assert(0);
         break;
     }
-    debug_log_state();
+    debug_log_state("before_rollback_leave");
     return 0;
 }
 
 int trrep::transaction_context::after_rollback()
 {
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("after_rollback_enter");
     assert(state() == s_aborting ||
            state() == s_must_replay);
 
@@ -384,7 +369,7 @@ int trrep::transaction_context::after_rollback()
     // during actual rollback. If the transaction has been ordered,
     // releasing the commit ordering critical section should be
     // also postponed until all resources have been released.
-    debug_log_state();
+    debug_log_state("after_rollback_leave");
     return 0;
 }
 
@@ -392,7 +377,7 @@ int trrep::transaction_context::after_statement()
 {
     int ret(0);
     trrep::unique_lock<trrep::mutex> lock(client_context_.mutex());
-    debug_log_state();
+    debug_log_state("after_statement_enter");
     assert(state() == s_executing ||
            state() == s_committed ||
            state() == s_aborted ||
@@ -446,7 +431,7 @@ int trrep::transaction_context::after_statement()
         cleanup();
     }
 
-    debug_log_state();
+    debug_log_state("after_statement_leave");
     return ret;
 }
 
@@ -458,7 +443,7 @@ void trrep::transaction_context::state(
 {
     assert(lock.owns_lock());
     static const char allowed[n_states][n_states] =
-        { /*  ex pr ce co oc ct cf ma ab ad mr re from/to */
+        { /*  ex pr ce co oc ct cf ma ab ad mr re */
             { 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0}, /* ex */
             { 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0}, /* pr */
             { 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0}, /* ce */
@@ -700,9 +685,7 @@ void trrep::transaction_context::clear_fragments()
 
 void trrep::transaction_context::cleanup()
 {
-    // std::cerr << "Cleanup transaction "
-    //        << client_context_.id().get()
-    //         << ": " << id_.get() << "\n";
+    debug_log_state("cleanup_enter");
     id_ = trrep::transaction_id::invalid();
     if (is_streaming())
     {
@@ -715,11 +698,17 @@ void trrep::transaction_context::cleanup()
     trx_meta_.stid.conn = trrep::client_id::invalid();
     certified_ = false;
     pa_unsafe_ = false;
+    debug_log_state("cleanup_leave");
 }
 
-void trrep::transaction_context::debug_log_state() const
+void trrep::transaction_context::debug_log_state(
+    const std::string& context TRREP_UNUSED)
+    const
 {
-    // std::cout << "client: " << client_context_.id().get()
-    //        << " trx: " << id_.get()
-    //         << " state: " << state_ << "\n";
+#if 0
+    std::cout << context
+              << ": client: " << client_context_.id().get()
+              << " trx: " << int64_t(id_.get())
+              << " state: " << trrep::to_string(state_) << "\n";
+#endif /* 0 */
 }
diff --git a/src/transaction_context.hpp b/src/transaction_context.hpp
index 4786232..7f92484 100644
--- a/src/transaction_context.hpp
+++ b/src/transaction_context.hpp
@@ -6,6 +6,7 @@
 #define TRREP_TRANSACTION_CONTEXT_HPP
 
 #include "provider.hpp"
+#include "server_context.hpp"
 #include "lock.hpp"
 
 #include <wsrep_api.h>
@@ -55,11 +56,10 @@ namespace trrep
             s_replaying
         };
         static const int n_states = s_replaying + 1;
+        enum state state() const
+        { return state_; }
+
         transaction_context(trrep::client_context& client_context);
-        transaction_context(trrep::client_context& client_context,
-                            const wsrep_ws_handle_t& ws_handle,
-                            const wsrep_trx_meta_t& trx_meta,
-                            uint32_t flags);
         ~transaction_context();
         // Accessors
         trrep::transaction_id id() const
@@ -68,8 +68,6 @@ namespace trrep
         bool active() const
         { return (id_ != trrep::transaction_id::invalid()); }
 
-        enum state state() const
-        { return state_; }
 
         void state(trrep::unique_lock<trrep::mutex>&, enum state);
 
@@ -99,6 +97,10 @@ namespace trrep
 
         int start_transaction(const trrep::transaction_id& id);
 
+        int start_transaction(const wsrep_ws_handle_t& ws_handle,
+                              const wsrep_trx_meta_t& trx_meta,
+                              uint32_t flags);
+
         int append_key(const trrep::key&);
 
         int append_data(const trrep::data&);
@@ -128,12 +130,15 @@ namespace trrep
             return flags_;
         }
     private:
+        transaction_context(const transaction_context&);
+        transaction_context operator=(const transaction_context&);
+
         int certify_fragment(trrep::unique_lock<trrep::mutex>&);
         int certify_commit(trrep::unique_lock<trrep::mutex>&);
         void remove_fragments();
         void clear_fragments();
         void cleanup();
-        void debug_log_state() const;
+        void debug_log_state(const std::string&) const;
         trrep::provider& provider_;
         trrep::client_context& client_context_;
         trrep::transaction_id id_;
diff --git a/src/transaction_context_test.cpp b/src/transaction_context_test.cpp
index ac6afb8..8e3f1a2 100644
--- a/src/transaction_context_test.cpp
+++ b/src/transaction_context_test.cpp
@@ -20,7 +20,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc)
                                   trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc,trrep::client_id(1),
                              trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -60,7 +60,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_2pc)
     trrep::mock_server_context sc("s1", "s1",
                                  trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -108,7 +108,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_rollback)
                                   trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc,trrep::client_id(1),
                              trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -144,7 +144,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc_bf_before_before_commit)
     trrep::mock_server_context sc("s1", "s1",
                                  trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -185,7 +185,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_2pc_bf_before_before_prepare)
     trrep::mock_server_context sc("s1", "s1",
                              trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -226,7 +226,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_2pc_bf_before_after_prepare)
     trrep::mock_server_context sc("s1", "s1",
                              trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -272,7 +272,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc_bf_during_before_commit_uncertified
     trrep::mock_server_context sc("s1", "s1",
                                  trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -315,7 +315,7 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc_bf_during_before_commit_certified)
     trrep::mock_server_context sc("s1", "s1",
                                  trrep::server_context::rm_sync);
     trrep::mock_client_context cc(sc, trrep::client_id(1), trrep::client_context::m_replicating);
-    trrep::transaction_context tc(cc);
+    trrep::transaction_context& tc(cc.transaction());
 
     // Verify initial state
     BOOST_REQUIRE(tc.active() == false);
@@ -355,9 +355,9 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc_applying)
     trrep::mock_client_context cc(sc,
                              trrep::client_id(1),
                              trrep::client_context::m_applier);
-    trrep::transaction_context tc(trrep_mock::applying_transaction(
-                                      cc, 1, 1,
-                                      WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
+    trrep::transaction_context& tc(trrep_mock::start_applying_transaction(
+                                       cc, 1, 1,
+                                       WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
 
     BOOST_REQUIRE(tc.active() == false);
     BOOST_REQUIRE(tc.start_transaction() == 0);
@@ -371,6 +371,9 @@ BOOST_AUTO_TEST_CASE(transaction_context_1pc_applying)
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_ordered_commit);
     BOOST_REQUIRE(tc.after_commit() == 0);
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_committed);
+    BOOST_REQUIRE(tc.after_statement() == 0);
+    BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_committed);
+    BOOST_REQUIRE(tc.active() == false);
 }
 
 BOOST_AUTO_TEST_CASE(transaction_context_2pc_applying)
@@ -380,9 +383,9 @@ BOOST_AUTO_TEST_CASE(transaction_context_2pc_applying)
     trrep::mock_client_context cc(sc,
                              trrep::client_id(1),
                              trrep::client_context::m_applier);
-    trrep::transaction_context tc(trrep_mock::applying_transaction(
-                                      cc, 1, 1,
-                                      WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
+    trrep::transaction_context& tc(trrep_mock::start_applying_transaction(
+                                       cc, 1, 1,
+                                       WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
 
     BOOST_REQUIRE(tc.active() == false);
     BOOST_REQUIRE(tc.start_transaction() == 0);
@@ -400,6 +403,9 @@ BOOST_AUTO_TEST_CASE(transaction_context_2pc_applying)
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_ordered_commit);
     BOOST_REQUIRE(tc.after_commit() == 0);
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_committed);
+    BOOST_REQUIRE(tc.after_statement() == 0);
+    BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_committed);
+    BOOST_REQUIRE(tc.active() == false);
 }
 
 BOOST_AUTO_TEST_CASE(transaction_context_applying_rollback)
@@ -409,9 +415,9 @@ BOOST_AUTO_TEST_CASE(transaction_context_applying_rollback)
     trrep::mock_client_context cc(sc,
                              trrep::client_id(1),
                              trrep::client_context::m_applier);
-    trrep::transaction_context tc(trrep_mock::applying_transaction(
-                                      cc, 1, 1,
-                                      WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
+    trrep::transaction_context& tc(trrep_mock::start_applying_transaction(
+                                       cc, 1, 1,
+                                       WSREP_FLAG_TRX_START | WSREP_FLAG_TRX_END));
 
     BOOST_REQUIRE(tc.active() == false);
     BOOST_REQUIRE(tc.start_transaction() == 0);
@@ -423,4 +429,8 @@ BOOST_AUTO_TEST_CASE(transaction_context_applying_rollback)
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_aborting);
     BOOST_REQUIRE(tc.after_rollback() == 0);
     BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_aborted);
+    BOOST_REQUIRE(tc.after_statement() == 0);
+    BOOST_REQUIRE(tc.state() == trrep::transaction_context::s_aborted);
+    BOOST_REQUIRE(tc.active() == false);
+
 }