diff --git a/src/backend/access/transam/Makefile b/src/backend/access/transam/Makefile
index 94455b2..37523a1 100644
--- a/src/backend/access/transam/Makefile
+++ b/src/backend/access/transam/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = clog.o commit_ts.o multixact.o parallel.o rmgr.o slru.o subtrans.o \
 	timeline.o transam.o twophase.o twophase_rmgr.o varsup.o \
 	xact.o xlog.o xlogarchive.o xlogfuncs.o \
-	xloginsert.o xlogreader.o xlogutils.o
+	xloginsert.o xlogreader.o xlogutils.o xtm.o
 
 include $(top_srcdir)/src/backend/common.mk
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 3a58f1e..f195feb 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -38,6 +38,7 @@
 #include "access/xlog.h"
 #include "access/xloginsert.h"
 #include "access/xlogutils.h"
+#include "access/xtm.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
 
@@ -92,6 +93,12 @@ static void TransactionIdSetStatusBit(TransactionId xid, XidStatus status,
 static void set_status_by_pages(int nsubxids, TransactionId *subxids,
 					XidStatus status, XLogRecPtr lsn);
 
+void
+TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
+					TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
+{
+	TM->SetTransactionStatus(xid, nsubxids, subxids, status, lsn);
+}
 
 /*
  * TransactionIdSetTreeStatus
@@ -145,7 +152,7 @@ static void set_status_by_pages(int nsubxids, TransactionId *subxids,
  * cache yet.
  */
 void
-TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
+PgTransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
 					TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
 {
 	int			pageno = TransactionIdToPage(xid);		/* get page of parent */
@@ -391,6 +398,12 @@ TransactionIdSetStatusBit(TransactionId xid, XidStatus status, XLogRecPtr lsn, i
 XidStatus
 TransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn)
 {
+	return TM->GetTransactionStatus(xid, lsn);
+}
+
+XidStatus
+PgTransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn)
+{
 	int			pageno = TransactionIdToPage(xid);
 	int			byteno = TransactionIdToByte(xid);
 	int			bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 8c47e0f..500855c 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1411,15 +1411,21 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	 * callbacks will release the locks the transaction held.
 	 */
 	if (isCommit)
+	{
 		RecordTransactionCommitPrepared(xid,
 										hdr->nsubxacts, children,
 										hdr->ncommitrels, commitrels,
 										hdr->ninvalmsgs, invalmsgs,
 										hdr->initfileinval);
+		CallXactCallbacks(XACT_EVENT_COMMIT_PREPARED);
+	}
 	else
+	{
 		RecordTransactionAbortPrepared(xid,
 									   hdr->nsubxacts, children,
 									   hdr->nabortrels, abortrels);
+		CallXactCallbacks(XACT_EVENT_ABORT_PREPARED);
+	}
 
 	ProcArrayRemove(proc, latestXid);
 
@@ -2211,3 +2217,12 @@ RecordTransactionAbortPrepared(TransactionId xid,
 	 */
 	SyncRepWaitForLSN(recptr);
 }
+
+/*
+ * Return identified of current global transaction
+ */
+const char*
+GetLockedGlobalTransactionId(void)
+{
+	return MyLockedGxact ? MyLockedGxact->gid : NULL;
+}
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index cf3e964..476b555 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -19,6 +19,7 @@
 #include "access/transam.h"
 #include "access/xact.h"
 #include "access/xlog.h"
+#include "access/xtm.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -33,6 +34,11 @@
 /* pointer to "variable cache" in shared memory (set up by shmem.c) */
 VariableCache ShmemVariableCache = NULL;
 
+TransactionId
+GetNewTransactionId(bool isSubXact)
+{
+	return TM->GetNewTransactionId(isSubXact);
+}
 
 /*
  * Allocate the next XID for a new transaction or subtransaction.
@@ -45,7 +51,7 @@ VariableCache ShmemVariableCache = NULL;
  * issue a warning about XID wrap.
  */
 TransactionId
-GetNewTransactionId(bool isSubXact)
+PgGetNewTransactionId(bool isSubXact)
 {
 	TransactionId xid;
 
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 47312f6..42f36dd 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -301,7 +301,6 @@ static void AtCommit_Memory(void);
 static void AtStart_Cache(void);
 static void AtStart_Memory(void);
 static void AtStart_ResourceOwner(void);
-static void CallXactCallbacks(XactEvent event);
 static void CallSubXactCallbacks(SubXactEvent event,
 					 SubTransactionId mySubid,
 					 SubTransactionId parentSubid);
@@ -1909,6 +1908,7 @@ StartTransaction(void)
 	 */
 	s->state = TRANS_INPROGRESS;
 
+	CallXactCallbacks(XACT_EVENT_START);
 	ShowTransactionState("StartTransaction");
 }
 
@@ -3309,7 +3309,7 @@ UnregisterXactCallback(XactCallback callback, void *arg)
 	}
 }
 
-static void
+void
 CallXactCallbacks(XactEvent event)
 {
 	XactCallbackItem *item;
diff --git a/src/backend/access/transam/xtm.c b/src/backend/access/transam/xtm.c
new file mode 100644
index 0000000..212d30f
--- /dev/null
+++ b/src/backend/access/transam/xtm.c
@@ -0,0 +1,42 @@
+/*-------------------------------------------------------------------------
+ *
+ * xtm.c
+ *		PostgreSQL implementation of transaction manager protocol
+ *
+ * This module defines default iplementaiton of PostgreSQL transaction manager protocol
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/access/transam/xtm.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/transam.h"
+#include "access/xtm.h"
+
+TransactionId PgGetGlobalTransactionId(void)
+{
+	return InvalidTransactionId;
+}
+
+TransactionManager PgTM = {
+	PgTransactionIdGetStatus,
+	PgTransactionIdSetTreeStatus,
+	PgGetSnapshotData,
+	PgGetNewTransactionId,
+	PgGetOldestXmin,
+	PgTransactionIdIsInProgress,
+	PgGetGlobalTransactionId,
+	PgXidInMVCCSnapshot
+};
+
+TransactionManager* TM = &PgTM;
+
+TransactionManager* GetTransactionManager(void)
+{
+	return TM;
+}
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 0dc4117..5231bcb 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -51,6 +51,7 @@
 #include "access/twophase.h"
 #include "access/xact.h"
 #include "access/xlog.h"
+#include "access/xtm.h"
 #include "catalog/catalog.h"
 #include "miscadmin.h"
 #include "storage/proc.h"
@@ -961,6 +962,12 @@ ProcArrayApplyXidAssignment(TransactionId topxid,
 	LWLockRelease(ProcArrayLock);
 }
 
+bool
+TransactionIdIsInProgress(TransactionId xid)
+{
+	return TM->IsInProgress(xid);
+}
+
 /*
  * TransactionIdIsInProgress -- is given transaction running in some backend
  *
@@ -988,7 +995,7 @@ ProcArrayApplyXidAssignment(TransactionId topxid,
  * PGXACT again anyway; see GetNewTransactionId).
  */
 bool
-TransactionIdIsInProgress(TransactionId xid)
+PgTransactionIdIsInProgress(TransactionId xid)
 {
 	static TransactionId *xids = NULL;
 	int			nxids = 0;
@@ -1249,6 +1256,12 @@ TransactionIdIsActive(TransactionId xid)
 }
 
 
+TransactionId
+GetOldestXmin(Relation rel, bool ignoreVacuum)
+{
+	return TM->GetOldestXmin(rel, ignoreVacuum);
+}
+
 /*
  * GetOldestXmin -- returns oldest transaction that was running
  *					when any current transaction was started.
@@ -1298,7 +1311,7 @@ TransactionIdIsActive(TransactionId xid)
  * GetOldestXmin() move backwards, with no consequences for data integrity.
  */
 TransactionId
-GetOldestXmin(Relation rel, bool ignoreVacuum)
+PgGetOldestXmin(Relation rel, bool ignoreVacuum)
 {
 	ProcArrayStruct *arrayP = procArray;
 	TransactionId result;
@@ -1460,6 +1473,12 @@ GetMaxSnapshotSubxidCount(void)
 	return TOTAL_MAX_CACHED_SUBXIDS;
 }
 
+Snapshot
+GetSnapshotData(Snapshot snapshot)
+{
+	return TM->GetSnapshot(snapshot);
+}
+
 /*
  * GetSnapshotData -- returns information about running transactions.
  *
@@ -1496,7 +1515,7 @@ GetMaxSnapshotSubxidCount(void)
  * not statically allocated (see xip allocation below).
  */
 Snapshot
-GetSnapshotData(Snapshot snapshot)
+PgGetSnapshotData(Snapshot snapshot)
 {
 	ProcArrayStruct *arrayP = procArray;
 	TransactionId xmin;
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 6f66112..8a3da47 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -66,6 +66,7 @@
 #include "access/subtrans.h"
 #include "access/transam.h"
 #include "access/xact.h"
+#include "access/xtm.h"
 #include "access/xlog.h"
 #include "storage/bufmgr.h"
 #include "storage/procarray.h"
@@ -1454,6 +1455,12 @@ HeapTupleIsSurelyDead(HeapTuple htup, TransactionId OldestXmin)
 	return TransactionIdPrecedes(HeapTupleHeaderGetRawXmax(tuple), OldestXmin);
 }
 
+bool
+XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
+{
+	return TM->IsInSnapshot(xid, snapshot);
+}
+
 /*
  * XidInMVCCSnapshot
  *		Is the given XID still-in-progress according to the snapshot?
@@ -1464,8 +1471,8 @@ HeapTupleIsSurelyDead(HeapTuple htup, TransactionId OldestXmin)
  * TransactionIdIsCurrentTransactionId first, except for known-committed
  * XIDs which could not be ours anyway.
  */
-static bool
-XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
+bool
+PgXidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
 {
 	uint32		i;
 
diff --git a/src/include/access/clog.h b/src/include/access/clog.h
index c5fd480..43d5977 100644
--- a/src/include/access/clog.h
+++ b/src/include/access/clog.h
@@ -27,6 +27,7 @@ typedef int XidStatus;
 #define TRANSACTION_STATUS_COMMITTED		0x01
 #define TRANSACTION_STATUS_ABORTED			0x02
 #define TRANSACTION_STATUS_SUB_COMMITTED	0x03
+#define TRANSACTION_STATUS_UNKNOWN 	        0x03
 
 
 extern void TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
diff --git a/src/include/access/twophase.h b/src/include/access/twophase.h
index 71ddff7..7e1a672 100644
--- a/src/include/access/twophase.h
+++ b/src/include/access/twophase.h
@@ -56,4 +56,6 @@ extern void CheckPointTwoPhase(XLogRecPtr redo_horizon);
 
 extern void FinishPreparedTransaction(const char *gid, bool isCommit);
 
+extern const char* GetLockedGlobalTransactionId(void);
+
 #endif   /* TWOPHASE_H */
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index cb1c2db..07e576b 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -77,6 +77,7 @@ extern bool MyXactAccessedTempRel;
  */
 typedef enum
 {
+	XACT_EVENT_START,
 	XACT_EVENT_COMMIT,
 	XACT_EVENT_PARALLEL_COMMIT,
 	XACT_EVENT_ABORT,
@@ -84,7 +85,9 @@ typedef enum
 	XACT_EVENT_PREPARE,
 	XACT_EVENT_PRE_COMMIT,
 	XACT_EVENT_PARALLEL_PRE_COMMIT,
-	XACT_EVENT_PRE_PREPARE
+	XACT_EVENT_PRE_PREPARE,
+	XACT_EVENT_COMMIT_PREPARED,
+	XACT_EVENT_ABORT_PREPARED
 } XactEvent;
 
 typedef void (*XactCallback) (XactEvent event, void *arg);
@@ -100,6 +103,8 @@ typedef enum
 typedef void (*SubXactCallback) (SubXactEvent event, SubTransactionId mySubid,
 									SubTransactionId parentSubid, void *arg);
 
+void CallXactCallbacks(XactEvent event);
+
 
 /* ----------------
  *		transaction-related XLOG entries
diff --git a/src/include/access/xtm.h b/src/include/access/xtm.h
new file mode 100644
index 0000000..0ccc858
--- /dev/null
+++ b/src/include/access/xtm.h
@@ -0,0 +1,68 @@
+/*
+ * xtm.h
+ *
+ * PostgreSQL transaction-commit-log manager
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/xtm.h
+ */
+#ifndef XTM_H
+#define XTM_H
+
+#include "access/clog.h"
+#include "utils/snapmgr.h"
+#include "utils/relcache.h"
+
+typedef struct
+{
+	/* Get current transaction status (encapsulation of TransactionIdGetStatus in clog.c) */
+	XidStatus (*GetTransactionStatus)(TransactionId xid, XLogRecPtr *lsn);
+
+	/* Set current transaction status (encapsulation of TransactionIdGetStatus in clog.c) */
+	void (*SetTransactionStatus)(TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
+
+	/* Get current transaction snaphot (encapsulation of GetSnapshotData in procarray.c) */
+	Snapshot (*GetSnapshot)(Snapshot snapshot);
+
+	/* Assign new Xid to transaction (encapsulation of GetNewTransactionId in varsup.c) */
+	TransactionId (*GetNewTransactionId)(bool isSubXact);
+
+	/* Get oldest transaction Xid that was running when any current transaction was started (encapsulation of GetOldestXmin in procarray.c) */
+	TransactionId (*GetOldestXmin)(Relation rel, bool ignoreVacuum);
+
+	/* Check if current transaction is not yet completed (encapsulation of TransactionIdIsInProgress in procarray.c) */
+	bool (*IsInProgress)(TransactionId xid);
+
+	/* Get global transaction XID: returns XID of current transaction if it is global, InvalidTransactionId otherwise */
+	TransactionId (*GetGlobalTransactionId)(void);
+
+	/* Is the given XID still-in-progress according to the snapshot (encapsulation of XidInMVCCSnapshot in tqual.c) */
+	bool (*IsInSnapshot)(TransactionId xid, Snapshot snapshot);
+} TransactionManager;
+
+/* Get pointer to transaction manager: actually returns content of TM variable */
+TransactionManager* GetTransactionManager(void);
+
+extern TransactionManager* TM;  /* Current transaction manager (can be substituted by extensions) */
+extern TransactionManager PgTM; /* Standard PostgreSQL transaction manager */
+
+/* Standard PostgreSQL function implementing TM interface */
+extern bool PgXidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
+
+extern void PgTransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
+										TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
+extern XidStatus PgTransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn);
+
+extern Snapshot PgGetSnapshotData(Snapshot snapshot);
+
+extern TransactionId PgGetOldestXmin(Relation rel, bool ignoreVacuum);
+
+extern bool PgTransactionIdIsInProgress(TransactionId xid);
+
+extern TransactionId PgGetGlobalTransactionId(void);
+
+extern TransactionId PgGetNewTransactionId(bool isSubXact);
+
+#endif