diff --git a/src/HashedObject.cpp b/src/HashedObject.cpp
index ceb7a1b2a5..faaf870ae8 100644
--- a/src/HashedObject.cpp
+++ b/src/HashedObject.cpp
@@ -57,8 +57,13 @@ bool HashedObject::store(HashedObjectType type, uint32 index, const std::vector<
 	sql.append(obj);
 	sql.append(");");
 
+	std::string exists =
+		boost::str(boost::format("SELECT ObjType FROM CommittedObject WHERE Hash = '%s';") % hash.GetHex());
+
 	ScopedLock sl(theApp->getHashNodeDB()->getDBLock());
 	Database* db = theApp->getHashNodeDB()->getDB();
+	if (SQL_EXISTS(db, exists))
+		return false;
 	return db->executeSQL(sql);
 }
 
@@ -73,7 +78,7 @@ bool HashedObject::store() const
 HashedObject::pointer HashedObject::retrieve(const uint256& hash)
 {
 	if (!theApp || !theApp->getHashNodeDB()) return HashedObject::pointer();
-	std::string sql = "SELECT * from CommittedObjects WHERE Hash='";
+	std::string sql = "SELECT * FROM CommittedObjects WHERE Hash='";
 	sql.append(hash.GetHex());
 	sql.append("';");
 
@@ -119,4 +124,14 @@ HashedObject::pointer HashedObject::retrieve(const uint256& hash)
 	return obj;
 }
 
+HashedObjectBulkWriter::HashedObjectBulkWriter() : sl(theApp->getHashNodeDB()->getDBLock())
+{
+	theApp->getHashNodeDB()->getDB()->executeSQL("BEGIN TRANSACTION;");
+}
+
+HashedObjectBulkWriter::~HashedObjectBulkWriter()
+{
+	theApp->getHashNodeDB()->getDB()->executeSQL("END TRANSACTION;");
+}
+
 // vim:ts=4
diff --git a/src/HashedObject.h b/src/HashedObject.h
index 7234082c40..6a0fa28693 100644
--- a/src/HashedObject.h
+++ b/src/HashedObject.h
@@ -3,18 +3,17 @@
 
 #include <vector>
 
-#include <boost/shared_ptr.hpp>
-
 #include "types.h"
 #include "uint256.h"
+#include "ScopedLock.h"
 
 enum HashedObjectType
 {
-	UNKNOWN=0,
-	LEDGER=1,
-	TRANSACTION=2,
-	ACCOUNT_NODE=3,
-	TRANSACTION_NODE=4
+	UNKNOWN = 0,
+	LEDGER = 1,
+	TRANSACTION = 2,
+	ACCOUNT_NODE = 3,
+	TRANSACTION_NODE = 4
 };
 
 class HashedObject
@@ -37,10 +36,27 @@ public:
 	const std::vector<unsigned char>& getData() { return mData; }
 
 	bool store() const;
+
 	static bool store(HashedObjectType type, uint32 index, const std::vector<unsigned char>& data,
 		const uint256& hash);
 
 	static HashedObject::pointer retrieve(const uint256& hash);
 };
 
+class HashedObjectBulkWriter
+{
+protected:
+	ScopedLock sl;
+
+public:
+
+	HashedObjectBulkWriter();
+	~HashedObjectBulkWriter();
+
+	bool store(HashedObjectType type, uint32 index, const std::vector<unsigned char>& data, const uint256& hash)
+	{ return HashedObject::store(type, index, data, hash); }
+	HashedObject::pointer retrieve(const uint256& hash)
+	{ return HashedObject::retrieve(hash); }
+};
+
 #endif
diff --git a/src/Ledger.cpp b/src/Ledger.cpp
index 5549c23433..e583647a6a 100644
--- a/src/Ledger.cpp
+++ b/src/Ledger.cpp
@@ -20,11 +20,8 @@
 
 Ledger::Ledger(const NewcoinAddress& masterID, uint64 startAmount) : mTotCoins(startAmount),
 	mCloseTime(0), mLedgerSeq(0), mLedgerInterval(LEDGER_INTERVAL), mClosed(false), mValidHash(false),
-	mAccepted(false), mImmutable(false)
+	mAccepted(false), mImmutable(false), mTransactionMap(new SHAMap()), mAccountStateMap(new SHAMap())
 {
-	mTransactionMap = boost::make_shared<SHAMap>();
-	mAccountStateMap = boost::make_shared<SHAMap>();
-
 	// special case: put coins in root account
 	AccountState::pointer startAccount = boost::make_shared<AccountState>(masterID);
 	startAccount->peekSLE().setIFieldAmount(sfBalance, startAmount);
@@ -263,10 +260,11 @@ void Ledger::saveAcceptedLedger(Ledger::pointer ledger)
 	theApp->getLedgerDB()->getDB()->executeSQL(sql);
 
 	// write out dirty nodes
-	while(ledger->mTransactionMap->flushDirty(64, TRANSACTION_NODE, ledger->mLedgerSeq))
+	while(ledger->mTransactionMap->flushDirty(256, TRANSACTION_NODE, ledger->mLedgerSeq))
 	{ ; }
-	while(ledger->mAccountStateMap->flushDirty(64, ACCOUNT_NODE, ledger->mLedgerSeq))
+	while(ledger->mAccountStateMap->flushDirty(256, ACCOUNT_NODE, ledger->mLedgerSeq))
 	{ ; }
+	ledger->disarmDirty();
 
 	SHAMap& txSet = *ledger->peekTransactionMap();
 	Database *db = theApp->getTxnDB()->getDB();
diff --git a/src/Ledger.h b/src/Ledger.h
index 598c148b2d..482fb27ba3 100644
--- a/src/Ledger.h
+++ b/src/Ledger.h
@@ -60,6 +60,8 @@ public:
 
 
 private:
+	static uint64 sGenesisClose;
+
 	uint256		mHash, mParentHash, mTransHash, mAccountHash;
 	uint64		mTotCoins;
 	uint64		mCloseTime; // when this ledger closes
@@ -67,8 +69,6 @@ private:
 	uint16		mLedgerInterval;
 	bool		mClosed, mValidHash, mAccepted, mImmutable;
 
-	static uint64 sGenesisClose;
-
 	SHAMap::pointer mTransactionMap, mAccountStateMap;
 
 	mutable boost::recursive_mutex mLock;
@@ -102,6 +102,8 @@ public:
 	bool isClosed()		{ return mClosed; }
 	bool isAccepted()	{ return mAccepted; }
 	bool isImmutable()	{ return mImmutable; }
+	void armDirty()		{ mTransactionMap->armDirty();		mAccountStateMap->armDirty(); }
+	void disarmDirty()	{ mTransactionMap->disarmDirty();	mAccountStateMap->disarmDirty(); }
 
 	// This ledger has closed, will never be accepted, and is accepting
 	// new transactions to be re-repocessed when do accept a new last-closed ledger
diff --git a/src/LedgerConsensus.cpp b/src/LedgerConsensus.cpp
index a129ca071d..4fc9ced246 100644
--- a/src/LedgerConsensus.cpp
+++ b/src/LedgerConsensus.cpp
@@ -752,6 +752,7 @@ void LedgerConsensus::accept(SHAMap::pointer set)
 	Log(lsDEBUG) << "Previous LCL " << mPrevLedgerHash.GetHex();
 
 	Ledger::pointer newLCL = boost::make_shared<Ledger>(false, boost::ref(*mPreviousLedger));
+	newLCL->armDirty();
 
 #ifdef DEBUG
 	Json::StyledStreamWriter ssw;
diff --git a/src/SHAMap.cpp b/src/SHAMap.cpp
index 8811dcce67..987a088d31 100644
--- a/src/SHAMap.cpp
+++ b/src/SHAMap.cpp
@@ -629,6 +629,12 @@ bool SHAMap::fetchNode(const uint256& hash, std::vector<unsigned char>& data)
 	return true;
 }
 
+void SHAMap::armDirty()
+{ // begin saving dirty nodes
+	++mSeq;
+	mDirtyNodes = boost::make_shared< boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer> >();
+}
+
 int SHAMap::flushDirty(int maxNodes, HashedObjectType t, uint32 seq)
 {
 	int flushed = 0;
@@ -636,37 +642,45 @@ int SHAMap::flushDirty(int maxNodes, HashedObjectType t, uint32 seq)
 
 	if(mDirtyNodes)
 	{
-		while (!mDirtyNodes->empty())
+		HashedObjectBulkWriter bw;
+		boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer>& dirtyNodes = *mDirtyNodes;
+		boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer>::iterator it = dirtyNodes.begin();
+		while (it != dirtyNodes.end())
 		{
-			SHAMapTreeNode::pointer& din = mDirtyNodes->begin()->second;
 			s.erase();
-			din->addRaw(s);
-			HashedObject::store(t, seq, s.peekData(), s.getSHA512Half());
-			mDirtyNodes->erase(mDirtyNodes->begin());
-			if(flushed++>=maxNodes) return flushed;
+			it->second->addRaw(s);
+			bw.store(t, seq, s.peekData(), s.getSHA512Half());
+			if (flushed++ >= maxNodes)
+				return flushed;
+			it = dirtyNodes.erase(it);
 		}
 	}
 
 	return flushed;
 }
 
+void SHAMap::disarmDirty()
+{ // stop saving dirty nodes
+	mDirtyNodes = boost::shared_ptr< boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer> >();
+}
+
 SHAMapTreeNode::pointer SHAMap::getNode(const SHAMapNode& nodeID)
 {
 	boost::recursive_mutex::scoped_lock sl(mLock);
 
-	SHAMapTreeNode::pointer node=checkCacheNode(nodeID);
-	if(node) return node;
+	SHAMapTreeNode::pointer node = checkCacheNode(nodeID);
+	if (node) return node;
 
-	node=root;
-	while(nodeID!=*node)
+	node = root;
+	while (nodeID != *node)
 	{
-		int branch=node->selectBranch(nodeID.getNodeID());
-		assert(branch>=0);
-		if( (branch<0) || (node->isEmptyBranch(branch)) )
+		int branch = node->selectBranch(nodeID.getNodeID());
+		assert(branch >= 0);
+		if ((branch < 0) || node->isEmptyBranch(branch))
 			return SHAMapTreeNode::pointer();
 
-		node=getNode(node->getChildNodeID(branch), node->getChildHash(branch), false);
-		if(!node) throw SHAMapException(MissingNode);
+		node = getNode(node->getChildNodeID(branch), node->getChildHash(branch), false);
+		if (!node) throw SHAMapException(MissingNode);
 	}
 	return node;
 }
diff --git a/src/SHAMap.h b/src/SHAMap.h
index 8851abbf1f..8dda9db8d0 100644
--- a/src/SHAMap.h
+++ b/src/SHAMap.h
@@ -244,7 +244,7 @@ private:
 	mutable boost::recursive_mutex mLock;
 	boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer> mTNByID;
 
-	boost::shared_ptr<std::map<SHAMapNode, SHAMapTreeNode::pointer> > mDirtyNodes;
+	boost::shared_ptr< boost::unordered_map<SHAMapNode, SHAMapTreeNode::pointer> > mDirtyNodes;
 
 	SHAMapTreeNode::pointer root;
 
@@ -329,7 +329,9 @@ public:
 	// return value: true=successfully completed, false=too different
 	bool compare(SHAMap::pointer otherMap, SHAMapDiff& differences, int maxCount);
 
+	void armDirty();
 	int flushDirty(int maxNodes, HashedObjectType t, uint32 seq);
+	void disarmDirty();
 
 	void setSeq(uint32 seq)		{ mSeq = seq; }
 	uint32 getSeq()				{ return mSeq; }
diff --git a/src/ScopedLock.h b/src/ScopedLock.h
index e0e65ddfac..1fd1ee6082 100644
--- a/src/ScopedLock.h
+++ b/src/ScopedLock.h
@@ -2,7 +2,6 @@
 #define __SCOPEDLOCKHOLDER__
 
 #include <boost/thread/recursive_mutex.hpp>
-#include <boost/interprocess/sync/scoped_lock.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/make_shared.hpp>
 #include <boost/ref.hpp>
@@ -13,11 +12,11 @@
 class ScopedLock
 {
 protected:
-	mutable boost::shared_ptr<boost::interprocess::scoped_lock<boost::recursive_mutex> > mHolder;
+	mutable boost::shared_ptr<boost::recursive_mutex::scoped_lock> mHolder;
 
 public:
 	ScopedLock(boost::recursive_mutex& mutex) :
-		mHolder(boost::make_shared<boost::interprocess::scoped_lock<boost::recursive_mutex> >(boost::ref(mutex)))
+		mHolder(boost::make_shared<boost::recursive_mutex::scoped_lock>(boost::ref(mutex)))
 	{ ;	}
 	void lock() const
 	{