diff --git a/hyracks-storage-am-btree/src/main/java/edu/uci/ics/hyracks/storage/am/btree/impls/BTree.java b/hyracks-storage-am-btree/src/main/java/edu/uci/ics/hyracks/storage/am/btree/impls/BTree.java
index b90a89a..846af3a 100644
--- a/hyracks-storage-am-btree/src/main/java/edu/uci/ics/hyracks/storage/am/btree/impls/BTree.java
+++ b/hyracks-storage-am-btree/src/main/java/edu/uci/ics/hyracks/storage/am/btree/impls/BTree.java
@@ -868,6 +868,7 @@
         return IndexType.BTREE;
     }
     
+    @Override
     public int getFileId() {
     	return fileId;
     }
diff --git a/hyracks-storage-am-common/src/main/java/edu/uci/ics/hyracks/storage/am/common/api/ITreeIndex.java b/hyracks-storage-am-common/src/main/java/edu/uci/ics/hyracks/storage/am/common/api/ITreeIndex.java
index 1c9dca3..1def8db 100644
--- a/hyracks-storage-am-common/src/main/java/edu/uci/ics/hyracks/storage/am/common/api/ITreeIndex.java
+++ b/hyracks-storage-am-common/src/main/java/edu/uci/ics/hyracks/storage/am/common/api/ITreeIndex.java
@@ -105,4 +105,9 @@
 	 * @return An enum of the concrete type of this index.
 	 */
 	public IndexType getIndexType();
+	
+	/**
+     * @return The file id of this index.
+     */
+    public int getFileId();
 }
diff --git a/hyracks-storage-am-lsm-common/pom.xml b/hyracks-storage-am-lsm-common/pom.xml
index 836b4a2..6dd4381 100644
--- a/hyracks-storage-am-lsm-common/pom.xml
+++ b/hyracks-storage-am-lsm-common/pom.xml
@@ -32,6 +32,13 @@
   		<scope>compile</scope>
   	</dependency>
   	<dependency>
+  		<groupId>edu.uci.ics.hyracks</groupId>
+  		<artifactId>hyracks-storage-am-btree</artifactId>
+  		<version>0.2.0-SNAPSHOT</version>
+  		<type>jar</type>
+  		<scope>compile</scope>
+  	</dependency>
+  	<dependency>
   		<groupId>junit</groupId>
   		<artifactId>junit</artifactId>
   		<version>4.8.1</version>
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMTree.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMTree.java
index 9775484..e64a56e 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMTree.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/api/ILSMTree.java
@@ -1,9 +1,11 @@
 package edu.uci.ics.hyracks.storage.am.lsm.common.api;
 
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
+import edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
 
 public interface ILSMTree extends ITreeIndex {
-    public void merge() throws Exception;
-    
-    public void flush() throws Exception;
+    public void merge() throws HyracksDataException, TreeIndexException;
+
+    public void flush() throws HyracksDataException, TreeIndexException;
 }
diff --git a/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/BTreeFactory.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BTreeFactory.java
similarity index 89%
rename from hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/BTreeFactory.java
rename to hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BTreeFactory.java
index 98824ab..090b49f 100644
--- a/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/BTreeFactory.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/BTreeFactory.java
@@ -1,11 +1,10 @@
-package edu.uci.ics.hyracks.storage.am.lsm.rtree.impls;
+package edu.uci.ics.hyracks.storage.am.lsm.common.impls;
 
 import edu.uci.ics.hyracks.storage.am.btree.impls.BTree;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
 import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndexFrameFactory;
 import edu.uci.ics.hyracks.storage.am.common.freepage.LinkedListFreePageManagerFactory;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.TreeFactory;
 import edu.uci.ics.hyracks.storage.common.buffercache.IBufferCache;
 
 public class BTreeFactory extends TreeFactory {
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMTree.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMTree.java
new file mode 100644
index 0000000..978fb1b
--- /dev/null
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMTree.java
@@ -0,0 +1,166 @@
+/*
+ * Copyright 2009-2010 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package edu.uci.ics.hyracks.storage.am.lsm.common.impls;
+
+import java.io.File;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.hyracks.api.io.FileReference;
+import edu.uci.ics.hyracks.storage.am.btree.impls.BTree;
+import edu.uci.ics.hyracks.storage.am.common.api.IIndexOpContext;
+import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndex;
+import edu.uci.ics.hyracks.storage.am.common.api.ITreeIndexFrameFactory;
+import edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
+import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMFileNameManager;
+import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMTree;
+import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
+import edu.uci.ics.hyracks.storage.common.buffercache.IBufferCache;
+import edu.uci.ics.hyracks.storage.common.file.IFileMapProvider;
+
+public abstract class LSMTree implements ILSMTree {
+    protected static final long AFTER_MERGE_CLEANUP_SLEEP = 100;
+
+    // In-memory components.
+    protected final BTree memBTree;
+    protected final InMemoryFreePageManager memFreePageManager;
+
+    // On-disk components.
+    protected final ILSMFileNameManager fileNameManager;
+    // For creating BTree's used in flush and merge.
+    protected final BTreeFactory diskBTreeFactory;
+
+    protected final IBufferCache diskBufferCache;
+    protected final IFileMapProvider diskFileMapProvider;
+    protected LinkedList<BTree> diskBTrees = new LinkedList<BTree>();
+
+    protected final MultiComparator cmp;
+
+    // For synchronizing all operations with flushes.
+    // Currently, all operations block during a flush.
+    private int threadRefCount;
+    protected boolean flushFlag;
+
+    // For synchronizing searchers with a concurrent merge.
+    protected AtomicBoolean isMerging = new AtomicBoolean(false);
+    protected AtomicInteger searcherRefCountA = new AtomicInteger(0);
+    protected AtomicInteger searcherRefCountB = new AtomicInteger(0);
+    // Represents the current number of searcher threads that are operating on
+    // the unmerged on-disk BTrees.
+    // We alternate between searcherRefCountA and searcherRefCountB.
+    protected AtomicInteger searcherRefCount = searcherRefCountA;
+
+    public LSMTree(IBufferCache memBufferCache, InMemoryFreePageManager memFreePageManager,
+            ITreeIndexFrameFactory btreeInteriorFrameFactory, ITreeIndexFrameFactory btreeLeafFrameFactory,
+            ILSMFileNameManager fileNameManager, BTreeFactory diskBTreeFactory, IFileMapProvider diskFileMapProvider,
+            int fieldCount, MultiComparator cmp) {
+        memBTree = new BTree(memBufferCache, fieldCount, cmp, memFreePageManager, btreeInteriorFrameFactory,
+                btreeLeafFrameFactory);
+        this.memFreePageManager = memFreePageManager;
+        this.diskBufferCache = diskBTreeFactory.getBufferCache();
+        this.diskFileMapProvider = diskFileMapProvider;
+        this.diskBTreeFactory = diskBTreeFactory;
+        this.cmp = cmp;
+        this.diskBTrees = new LinkedList<BTree>();
+        this.threadRefCount = 0;
+        this.flushFlag = false;
+        this.fileNameManager = fileNameManager;
+    }
+
+    @Override
+    public void create(int indexFileId) throws HyracksDataException {
+        memBTree.create(indexFileId);
+    }
+
+    @Override
+    public void close() throws HyracksDataException {
+        for (BTree btree : diskBTrees) {
+            diskBufferCache.closeFile(btree.getFileId());
+            btree.close();
+        }
+        diskBTrees.clear();
+        memBTree.close();
+    }
+
+    public void threadEnter() {
+        threadRefCount++;
+    }
+
+    public void threadExit() throws HyracksDataException, TreeIndexException {
+        synchronized (this) {
+            threadRefCount--;
+            // Check if we've reached or exceeded the maximum number of pages.
+            if (!flushFlag && memFreePageManager.isFull()) {
+                flushFlag = true;
+            }
+            // Flush will only be handled by last exiting thread.
+            if (flushFlag && threadRefCount == 0) {
+                flush();
+                flushFlag = false;
+            }
+        }
+    }
+
+    protected void cleanupTrees(List<ITreeIndex> mergingDiskTrees) throws HyracksDataException {
+        for (ITreeIndex oldTree : mergingDiskTrees) {
+            oldTree.close();
+            FileReference fileRef = diskFileMapProvider.lookupFileName(oldTree.getFileId());
+            diskBufferCache.closeFile(oldTree.getFileId());
+            diskBufferCache.deleteFile(oldTree.getFileId());
+            fileRef.getFile().delete();
+        }
+    }
+    
+    protected void resetMemBTree() throws HyracksDataException {
+        memFreePageManager.reset();
+        memBTree.create(memBTree.getFileId());
+    }
+
+    protected ITreeIndex createFlushTargetTree(String fileName) throws HyracksDataException {
+        return createDiskTree(diskBTreeFactory, fileName, true);
+    }
+
+    protected ITreeIndex createMergeTargetTree(String fileName) throws HyracksDataException {
+        return createDiskTree(diskBTreeFactory, fileName, true);
+    }
+
+    protected ITreeIndex createDiskTree(TreeFactory diskTreeFactory, String fileName, boolean createTree)
+            throws HyracksDataException {
+        // Register the new tree file.
+        FileReference file = new FileReference(new File(fileName));
+        // File will be deleted during cleanup of merge().
+        diskBufferCache.createFile(file);
+        int diskTreeFileId = diskFileMapProvider.lookupFileId(file);
+        // File will be closed during cleanup of merge().
+        diskBufferCache.openFile(diskTreeFileId);
+        // Create new tree instance.
+        ITreeIndex diskTree = diskTreeFactory.createIndexInstance(diskTreeFileId);
+        if (createTree) {
+            diskTree.create(diskTreeFileId);
+        }
+        // Tree will be closed during cleanup of merge().
+        diskTree.open(diskTreeFileId);
+        return diskTree;
+    }
+
+    @Override
+    public abstract void flush() throws HyracksDataException, TreeIndexException;
+
+}
diff --git a/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java b/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
index 9d0fea3..67c4d53 100644
--- a/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
+++ b/hyracks-storage-am-lsm-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/impls/LSMRTree.java
@@ -8,11 +8,9 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.ListIterator;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
-import edu.uci.ics.hyracks.api.io.FileReference;
 import edu.uci.ics.hyracks.dataflow.common.data.accessors.ITupleReference;
 import edu.uci.ics.hyracks.storage.am.btree.impls.BTree;
 import edu.uci.ics.hyracks.storage.am.btree.impls.RangePredicate;
@@ -28,9 +26,9 @@
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.IndexOp;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMFileNameManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMTree;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.TreeFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.BTreeFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMTree;
 import edu.uci.ics.hyracks.storage.am.rtree.api.IRTreeInteriorFrame;
 import edu.uci.ics.hyracks.storage.am.rtree.api.IRTreeLeafFrame;
 import edu.uci.ics.hyracks.storage.am.rtree.impls.RTree;
@@ -38,44 +36,23 @@
 import edu.uci.ics.hyracks.storage.common.buffercache.IBufferCache;
 import edu.uci.ics.hyracks.storage.common.file.IFileMapProvider;
 
-public class LSMRTree implements ILSMTree {
-    private static final long AFTER_MERGE_CLEANUP_SLEEP = 100;
+public class LSMRTree extends LSMTree {
 
     // In-memory components.
-    private RTree memRTree;
-    private final BTree memBTree;
-    private final InMemoryFreePageManager memFreePageManager;
-    private int rtreeFileId;
-    private int btreeFileId;
+    private final RTree memRTree;
+    private final static int MEM_RTREE_FILE_ID = 0;
+    private final static int MEM_BTREE_FILE_ID = 1;
 
     // On-disk components.
-    private final ILSMFileNameManager fileNameManager;
+    // For creating RTree's used in flush and merge.
     private final RTreeFactory diskRTreeFactory;
-    private final BTreeFactory diskBTreeFactory;
-    private final IBufferCache diskBufferCache;
-    private final IFileMapProvider diskFileMapProvider;
     private LinkedList<RTree> diskRTrees = new LinkedList<RTree>();
-    private LinkedList<BTree> diskBTrees = new LinkedList<BTree>();
 
     // Common for in-memory and on-disk components.
     private final ITreeIndexFrameFactory rtreeInteriorFrameFactory;
     private final ITreeIndexFrameFactory btreeInteriorFrameFactory;
     private final ITreeIndexFrameFactory rtreeLeafFrameFactory;
     private final ITreeIndexFrameFactory btreeLeafFrameFactory;
-    private final MultiComparator btreeCmp;
-
-    // For dealing with concurrent accesses.
-    private int threadRefCount;
-    private boolean flushFlag;
-
-    // For synchronizing searchers with a concurrent merge.
-    private AtomicBoolean isMerging = new AtomicBoolean(false);
-    private AtomicInteger searcherRefCountA = new AtomicInteger(0);
-    private AtomicInteger searcherRefCountB = new AtomicInteger(0);
-    // Represents the current number of searcher threads that are operating on
-    // the unmerged on-disk RTrees and BTrees.
-    // We alternate between searcherRefCountA and searcherRefCountB.
-    private AtomicInteger searcherRefCount = searcherRefCountA;
 
     public LSMRTree(IBufferCache memBufferCache, InMemoryFreePageManager memFreePageManager,
             ITreeIndexFrameFactory rtreeInteriorFrameFactory, ITreeIndexFrameFactory rtreeLeafFrameFactory,
@@ -83,33 +60,23 @@
             ILSMFileNameManager fileNameManager, RTreeFactory diskRTreeFactory, BTreeFactory diskBTreeFactory,
             IFileMapProvider diskFileMapProvider, int fieldCount, MultiComparator rtreeCmp, MultiComparator btreeCmp) {
 
+        super(memBufferCache, memFreePageManager, btreeInteriorFrameFactory, btreeLeafFrameFactory, fileNameManager,
+                diskBTreeFactory, diskFileMapProvider, fieldCount, btreeCmp);
         memRTree = new RTree(memBufferCache, fieldCount, rtreeCmp, memFreePageManager, rtreeInteriorFrameFactory,
                 rtreeLeafFrameFactory);
-        memBTree = new BTree(memBufferCache, fieldCount, btreeCmp, memFreePageManager, btreeInteriorFrameFactory,
-                btreeLeafFrameFactory);
 
-        this.memFreePageManager = memFreePageManager;
         this.rtreeInteriorFrameFactory = rtreeInteriorFrameFactory;
         this.rtreeLeafFrameFactory = rtreeLeafFrameFactory;
         this.btreeInteriorFrameFactory = btreeInteriorFrameFactory;
         this.btreeLeafFrameFactory = btreeLeafFrameFactory;
 
-        this.diskBufferCache = diskRTreeFactory.getBufferCache();
-        this.diskFileMapProvider = diskFileMapProvider;
         this.diskRTreeFactory = diskRTreeFactory;
-        this.diskBTreeFactory = diskBTreeFactory;
-        this.btreeCmp = btreeCmp;
-        this.threadRefCount = 0;
-        this.flushFlag = false;
-        this.fileNameManager = fileNameManager;
-        this.rtreeFileId = 0;
-        this.btreeFileId = 1;
     }
 
     @Override
     public void create(int indexFileId) throws HyracksDataException {
-        memRTree.create(rtreeFileId);
-        memBTree.create(btreeFileId);
+        super.create(MEM_BTREE_FILE_ID);
+        memRTree.create(MEM_RTREE_FILE_ID);
     }
 
     /**
@@ -130,19 +97,19 @@
      */
     @Override
     public void open(int indexFileId) throws HyracksDataException {
-        memRTree.open(rtreeFileId);
-        memBTree.open(btreeFileId);
+        memRTree.open(MEM_RTREE_FILE_ID);
+        memBTree.open(MEM_BTREE_FILE_ID);
         File dir = new File(fileNameManager.getBaseDir());
         FilenameFilter rtreeFilter = new FilenameFilter() {
             public boolean accept(File dir, String name) {
-                return !name.startsWith(".") && !name.endsWith("btree");
+                return !name.startsWith(".") && name.endsWith("rtree");
             }
         };
         String[] rtreeFiles = dir.list(rtreeFilter);
 
         FilenameFilter btreeFilter = new FilenameFilter() {
             public boolean accept(File dir, String name) {
-                return !name.startsWith(".") && !name.endsWith("rtree");
+                return !name.startsWith(".") && name.endsWith("btree");
             }
         };
         String[] btreeFiles = dir.list(btreeFilter);
@@ -154,31 +121,26 @@
         Comparator<String> fileNameCmp = fileNameManager.getFileNameComparator();
         Arrays.sort(rtreeFiles, fileNameCmp);
         for (String fileName : rtreeFiles) {
-            RTree rtree = (RTree) createDiskTree(fileName, diskRTreeFactory, false);
+            RTree rtree = (RTree) createDiskTree(diskRTreeFactory, fileName, false);
             diskRTrees.add(rtree);
         }
 
         Arrays.sort(btreeFiles, fileNameCmp);
         for (String fileName : btreeFiles) {
-            BTree btree = (BTree) createDiskTree(fileName, diskBTreeFactory, false);
+            BTree btree = (BTree) createDiskTree(diskBTreeFactory, fileName, false);
             diskBTrees.add(btree);
         }
     }
 
     @Override
     public void close() throws HyracksDataException {
+        super.close();
         for (RTree rtree : diskRTrees) {
             diskBufferCache.closeFile(rtree.getFileId());
             rtree.close();
         }
-        for (BTree btree : diskBTrees) {
-            diskBufferCache.closeFile(btree.getFileId());
-            btree.close();
-        }
         diskRTrees.clear();
-        diskBTrees.clear();
         memRTree.close();
-        memBTree.close();
     }
 
     @Override
@@ -192,10 +154,10 @@
         // bulk loaded tree is "newer" than any other merged tree.
 
         String fileName = fileNameManager.getFlushFileName();
-        RTree diskRTree = (RTree) createDiskTree(fileName + "-rtree", diskRTreeFactory, true);
+        RTree diskRTree = (RTree) createDiskTree(diskRTreeFactory, fileName + "-rtree", true);
         // For each RTree, we require to have a buddy BTree. thus, we create an
         // empty BTree. This can be optimized later.
-        BTree diskBTree = (BTree) createDiskTree(fileName + "-btree", diskBTreeFactory, true);
+        BTree diskBTree = (BTree) createDiskTree(diskBTreeFactory, fileName + "-btree", true);
         LSMRTreeBulkLoadContext bulkLoadCtx = new LSMRTreeBulkLoadContext(diskRTree, diskBTree);
         bulkLoadCtx.beginBulkLoad(fillFactor);
         return bulkLoadCtx;
@@ -220,51 +182,55 @@
 
     @Override
     public ITreeIndexFrameFactory getLeafFrameFactory() {
-        // TODO Auto-generated method stub
         return null;
     }
 
     @Override
     public ITreeIndexFrameFactory getInteriorFrameFactory() {
-        // TODO Auto-generated method stub
         return null;
     }
 
     @Override
     public IFreePageManager getFreePageManager() {
-        // TODO Auto-generated method stub
         return null;
     }
 
     @Override
     public int getFieldCount() {
-        // TODO Auto-generated method stub
         return 0;
     }
 
     @Override
     public int getRootPageId() {
-        // TODO Auto-generated method stub
         return 0;
     }
 
     @Override
     public IndexType getIndexType() {
-        // TODO Auto-generated method stub
         return null;
     }
 
-    private void insert(ITupleReference tuple, LSMRTreeOpContext ctx) throws HyracksDataException, TreeIndexException {
-        boolean waitForFlush = false;
+    @Override
+    public int getFileId() {
+        return 0;
+    }
+
+    private void insertOrDelete(ITupleReference tuple, ITreeIndexAccessor accessor) throws HyracksDataException,
+            TreeIndexException {
+        boolean waitForFlush = true;
         do {
+            // Wait for ongoing flush to complete.
             synchronized (this) {
                 if (!flushFlag) {
+                    // Increments threadRefCount, to force a flush to wait for this operation to finish.
+                    // (a flush can only begin once threadRefCount == 0).
                     threadEnter();
+                    // Proceed with operation.
                     waitForFlush = false;
                 }
             }
-        } while (waitForFlush == true);
-        ctx.memRTreeAccessor.insert(tuple);
+        } while (waitForFlush);
+        accessor.insert(tuple);
         try {
             threadExit();
         } catch (Exception e) {
@@ -272,25 +238,15 @@
         }
     }
 
+    private void insert(ITupleReference tuple, LSMRTreeOpContext ctx) throws HyracksDataException, TreeIndexException {
+        insertOrDelete(tuple, ctx.memRTreeAccessor);
+    }
+
     private void delete(ITupleReference tuple, LSMRTreeOpContext ctx) throws HyracksDataException, TreeIndexException {
-        boolean waitForFlush = false;
-        do {
-            synchronized (this) {
-                if (!flushFlag) {
-                    threadEnter();
-                    waitForFlush = false;
-                }
-            }
-        } while (waitForFlush == true);
-        ctx.memBTreeAccessor.insert(tuple);
-        try {
-            threadExit();
-        } catch (Exception e) {
-            e.printStackTrace();
-        }
+        insertOrDelete(tuple, ctx.memBTreeAccessor);
     }
 
-    private Pair<List<RTree>, List<BTree>> search(ITreeIndexCursor cursor, ISearchPredicate rtreeSearchPred,
+    private Pair<List<ITreeIndex>, List<ITreeIndex>> search(ITreeIndexCursor cursor, ISearchPredicate rtreeSearchPred,
             LSMRTreeOpContext ctx, boolean includeMemRTree) throws HyracksDataException, TreeIndexException {
         // If the search doesn't include the in-memory RTree, then we don't have
         // to synchronize with a flush.
@@ -315,8 +271,8 @@
         // flush adds another on-disk RTree.
         // Since this mode is only used for merging trees, it doesn't really
         // matter if the merge excludes the new on-disk RTree.
-        List<RTree> diskRTreesSnapshot = new ArrayList<RTree>();
-        List<BTree> diskBTreesSnapshot = new ArrayList<BTree>();
+        List<ITreeIndex> diskRTreesSnapshot = new ArrayList<ITreeIndex>();
+        List<ITreeIndex> diskBTreesSnapshot = new ArrayList<ITreeIndex>();
         AtomicInteger localSearcherRefCount = null;
         synchronized (diskRTrees) {
             diskRTreesSnapshot.addAll(diskRTrees);
@@ -341,17 +297,17 @@
             bTreeAccessors = new ITreeIndexAccessor[numDiskTrees];
         }
 
-        ListIterator<BTree> diskBTreesIter = diskBTreesSnapshot.listIterator();
+        ListIterator<ITreeIndex> diskBTreesIter = diskBTreesSnapshot.listIterator();
         while (diskBTreesIter.hasNext()) {
-            BTree diskBTree = diskBTreesIter.next();
+            BTree diskBTree = (BTree) diskBTreesIter.next();
             bTreeAccessors[diskBTreeIx] = diskBTree.createAccessor();
             diskBTreeIx++;
         }
 
         LSMRTreeSearchCursor lsmRTreeCursor = (LSMRTreeSearchCursor) cursor;
         LSMRTreeCursorInitialState initialState = new LSMRTreeCursorInitialState(numDiskTrees + 1,
-                rtreeLeafFrameFactory, rtreeInteriorFrameFactory, btreeLeafFrameFactory, btreeCmp, bTreeAccessors,
-                this, includeMemRTree, localSearcherRefCount);
+                rtreeLeafFrameFactory, rtreeInteriorFrameFactory, btreeLeafFrameFactory, cmp, bTreeAccessors, this,
+                includeMemRTree, localSearcherRefCount);
         lsmRTreeCursor.open(initialState, rtreeSearchPred);
 
         int cursorIx = 1;
@@ -364,50 +320,31 @@
 
         // Open cursors of on-disk RTrees
         ITreeIndexAccessor[] diskRTreeAccessors = new ITreeIndexAccessor[numDiskTrees];
-        ListIterator<RTree> diskRTreesIter = diskRTreesSnapshot.listIterator();
+        ListIterator<ITreeIndex> diskRTreesIter = diskRTreesSnapshot.listIterator();
 
         int diskRTreeIx = 0;
         while (diskRTreesIter.hasNext()) {
-            RTree diskRTree = diskRTreesIter.next();
+            RTree diskRTree = (RTree) diskRTreesIter.next();
             diskRTreeAccessors[diskRTreeIx] = diskRTree.createAccessor();
             diskRTreeAccessors[diskRTreeIx].search(lsmRTreeCursor.getCursor(cursorIx), rtreeSearchPred);
             cursorIx++;
             diskRTreeIx++;
         }
-        return new Pair<List<RTree>, List<BTree>>(diskRTreesSnapshot, diskBTreesSnapshot);
+        return new Pair<List<ITreeIndex>, List<ITreeIndex>>(diskRTreesSnapshot, diskBTreesSnapshot);
 
     }
 
-    private ITreeIndex createDiskTree(String fileName, TreeFactory diskTreeFactory, boolean createTree)
-            throws HyracksDataException {
-        // Register the new tree file.
-        FileReference file = new FileReference(new File(fileName));
-        // TODO: Delete the file during cleanup.
-        diskBufferCache.createFile(file);
-        int diskTreeFileId = diskFileMapProvider.lookupFileId(file);
-        // TODO: Close the file during cleanup.
-        diskBufferCache.openFile(diskTreeFileId);
-        // Create new tree instance.
-        ITreeIndex diskTree = diskTreeFactory.createIndexInstance(diskTreeFileId);
-        if (createTree) {
-            diskTree.create(diskTreeFileId);
-        }
-        // TODO: Close the tree during cleanup.
-        diskTree.open(diskTreeFileId);
-        return diskTree;
-    }
-
     @Override
     public void flush() throws HyracksDataException, TreeIndexException {
 
-        // scan the RTree
+        // scan the memory RTree
         ITreeIndexAccessor memRTreeAccessor = memRTree.createAccessor();
         ITreeIndexCursor rtreeScanCursor = memRTreeAccessor.createSearchCursor();
         SearchPredicate rtreeNullPredicate = new SearchPredicate(null, null);
         memRTreeAccessor.search(rtreeScanCursor, rtreeNullPredicate);
 
         String fileName = fileNameManager.getFlushFileName();
-        RTree diskRTree = (RTree) createDiskTree(fileName + "-rtree", diskRTreeFactory, true);
+        RTree diskRTree = (RTree) createDiskTree(diskRTreeFactory, fileName + "-rtree", true);
 
         // BulkLoad the tuples from the in-memory tree into the new disk RTree.
         IIndexBulkLoadContext rtreeBulkLoadCtx = diskRTree.beginBulkLoad(1.0f);
@@ -423,13 +360,13 @@
         }
         diskRTree.endBulkLoad(rtreeBulkLoadCtx);
 
-        // scan the BTree
+        // scan the memory BTree
         ITreeIndexAccessor memBTreeAccessor = memBTree.createAccessor();
         ITreeIndexCursor btreeScanCursor = memBTreeAccessor.createSearchCursor();
         RangePredicate btreeNullPredicate = new RangePredicate(null, null, true, true, null, null);
         memBTreeAccessor.search(btreeScanCursor, btreeNullPredicate);
 
-        BTree diskBTree = (BTree) createDiskTree(fileName + "-btree", diskBTreeFactory, true);
+        BTree diskBTree = (BTree) createDiskTree(diskBTreeFactory, fileName + "-btree", true);
 
         // BulkLoad the tuples from the in-memory tree into the new disk BTree.
         IIndexBulkLoadContext btreeBulkLoadCtx = diskBTree.beginBulkLoad(1.0f);
@@ -444,7 +381,7 @@
         }
         diskBTree.endBulkLoad(btreeBulkLoadCtx);
 
-        resetInMemoryTrees();
+        resetMemoryTrees();
 
         synchronized (diskRTrees) {
             diskRTrees.addFirst(diskRTree);
@@ -454,8 +391,8 @@
 
     @Override
     public void merge() throws HyracksDataException, TreeIndexException {
-        if (isMerging.get()) {
-            throw new TreeIndexException("Merge already in progress in LSM-RTree. Only one concurrent merge allowed.");
+        if (!isMerging.compareAndSet(false, true)) {
+            throw new TreeIndexException("Merge already in progress in LSMRTree. Only one concurrent merge allowed.");
         }
         isMerging.set(true);
 
@@ -467,14 +404,14 @@
         ITreeIndexCursor cursor = new LSMRTreeSearchCursor();
         SearchPredicate rtreeSearchPred = new SearchPredicate(null, null);
         // Scan the RTrees, ignoring the in-memory RTree.
-        Pair<List<RTree>, List<BTree>> mergingDiskTreesPair = search(cursor, rtreeSearchPred, ctx, false);
-        List<RTree> mergingDiskRTrees = mergingDiskTreesPair.getFirst();
-        List<BTree> mergingDiskBTrees = mergingDiskTreesPair.getSecond();
+        Pair<List<ITreeIndex>, List<ITreeIndex>> mergingDiskTreesPair = search(cursor, rtreeSearchPred, ctx, false);
+        List<ITreeIndex> mergingDiskRTrees = mergingDiskTreesPair.getFirst();
+        List<ITreeIndex> mergingDiskBTrees = mergingDiskTreesPair.getSecond();
 
         // Bulk load the tuples from all on-disk RTrees into the new RTree.
         String fileName = fileNameManager.getMergeFileName();
-        RTree mergedRTree = (RTree) createDiskTree(fileName + "-rtree", diskRTreeFactory, true);
-        BTree mergedBTree = (BTree) createDiskTree(fileName + "-btree", diskBTreeFactory, true);
+        RTree mergedRTree = (RTree) createDiskTree(diskRTreeFactory, fileName + "-rtree", true);
+        BTree mergedBTree = (BTree) createDiskTree(diskBTreeFactory, fileName + "-btree", true);
 
         IIndexBulkLoadContext bulkLoadCtx = mergedRTree.beginBulkLoad(1.0f);
         try {
@@ -522,57 +459,25 @@
         // Cleanup. At this point we have guaranteed that no searchers are
         // touching the old on-disk RTrees and BTrees (localSearcherRefCount ==
         // 0).
-        for (RTree oldRTree : mergingDiskRTrees) {
-            oldRTree.close();
-            FileReference fileRef = diskFileMapProvider.lookupFileName(oldRTree.getFileId());
-            diskBufferCache.closeFile(oldRTree.getFileId());
-            diskBufferCache.deleteFile(oldRTree.getFileId());
-            fileRef.getFile().delete();
-        }
-        for (BTree oldBTree : mergingDiskBTrees) {
-            oldBTree.close();
-            FileReference fileRef = diskFileMapProvider.lookupFileName(oldBTree.getFileId());
-            diskBufferCache.closeFile(oldBTree.getFileId());
-            diskBufferCache.deleteFile(oldBTree.getFileId());
-            fileRef.getFile().delete();
-        }
+        cleanupTrees(mergingDiskRTrees);
+        cleanupTrees(mergingDiskBTrees);
         isMerging.set(false);
 
     }
 
-    public void resetInMemoryTrees() throws HyracksDataException {
-        memFreePageManager.reset();
-        memRTree.create(rtreeFileId);
-        memBTree.create(btreeFileId);
+    public void resetMemoryTrees() throws HyracksDataException {
+        resetMemBTree();
+        memRTree.create(MEM_RTREE_FILE_ID);
     }
 
-    public void threadEnter() {
-        threadRefCount++;
-    }
-
-    public void threadExit() throws HyracksDataException, TreeIndexException {
-        synchronized (this) {
-            threadRefCount--;
-            // Check if we've reached or exceeded the maximum number of pages.
-            if (!flushFlag && memFreePageManager.isFull()) {
-                flushFlag = true;
-            }
-            // Flush will only be handled by last exiting thread.
-            if (flushFlag && threadRefCount == 0) {
-                flush();
-                flushFlag = false;
-            }
-        }
-    }
-
-    private LSMRTreeOpContext createOpContext() {
+    protected LSMRTreeOpContext createOpContext() {
 
         return new LSMRTreeOpContext((RTree.RTreeAccessor) memRTree.createAccessor(),
                 (IRTreeLeafFrame) rtreeLeafFrameFactory.createFrame(),
                 (IRTreeInteriorFrame) rtreeInteriorFrameFactory.createFrame(), memFreePageManager
                         .getMetaDataFrameFactory().createFrame(), 8, (BTree.BTreeAccessor) memBTree.createAccessor(),
                 btreeLeafFrameFactory, btreeInteriorFrameFactory, memFreePageManager.getMetaDataFrameFactory()
-                        .createFrame(), btreeCmp);
+                        .createFrame(), cmp);
     }
 
     private class LSMRTreeAccessor implements ITreeIndexAccessor {
@@ -621,12 +526,12 @@
 
         @Override
         public ITreeIndexCursor createDiskOrderScanCursor() {
-            throw new UnsupportedOperationException("DiskOrderScan not supported by LSM-RTree.");
+            throw new UnsupportedOperationException("DiskOrderScan not supported by LSMRTree.");
         }
 
         @Override
         public void diskOrderScan(ITreeIndexCursor cursor) throws HyracksDataException {
-            throw new UnsupportedOperationException("DiskOrderScan not supported by LSM-RTree.");
+            throw new UnsupportedOperationException("DiskOrderScan not supported by LSMRTree.");
         }
     }
 
diff --git a/hyracks-storage-am-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/rtree/impls/RTree.java b/hyracks-storage-am-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/rtree/impls/RTree.java
index 86cad34..79fbc72 100644
--- a/hyracks-storage-am-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/rtree/impls/RTree.java
+++ b/hyracks-storage-am-rtree/src/main/java/edu/uci/ics/hyracks/storage/am/rtree/impls/RTree.java
@@ -229,18 +229,21 @@
         }
     }
 
+    @Override
     public void open(int fileId) {
         this.fileId = fileId;
     }
 
+    @Override
     public void close() {
         fileId = -1;
     }
 
+    @Override
     public int getFileId() {
         return fileId;
     }
-    
+
     private RTreeOpContext createOpContext() {
         return new RTreeOpContext((IRTreeLeafFrame) leafFrameFactory.createFrame(),
                 (IRTreeInteriorFrame) interiorFrameFactory.createFrame(), freePageManager.getMetaDataFrameFactory()
@@ -325,7 +328,7 @@
                         incrementReadLatchesAcquired();
                     }
                 }
-                
+
                 if (pageId != rootPage && parentLsn < ctx.interiorFrame.getPageNsn()) {
                     // Concurrent split detected, go back to parent and
                     // re-choose
@@ -958,10 +961,12 @@
         ctx.cursor.open(ctx.cursorInitialState, (SearchPredicate) searchPred);
     }
 
+    @Override
     public ITreeIndexFrameFactory getInteriorFrameFactory() {
         return interiorFrameFactory;
     }
 
+    @Override
     public ITreeIndexFrameFactory getLeafFrameFactory() {
         return leafFrameFactory;
     }
@@ -970,6 +975,7 @@
         return cmp;
     }
 
+    @Override
     public IFreePageManager getFreePageManager() {
         return freePageManager;
     }
@@ -1084,13 +1090,12 @@
             rtree.delete(tuple, ctx);
         }
 
-		@Override
-		public ITreeIndexCursor createSearchCursor() {
-			return new RTreeSearchCursor(
-					(IRTreeInteriorFrame) interiorFrameFactory.createFrame(),
-					(IRTreeLeafFrame) leafFrameFactory.createFrame());
-		}
-        
+        @Override
+        public ITreeIndexCursor createSearchCursor() {
+            return new RTreeSearchCursor((IRTreeInteriorFrame) interiorFrameFactory.createFrame(),
+                    (IRTreeLeafFrame) leafFrameFactory.createFrame());
+        }
+
         @Override
         public void search(ITreeIndexCursor cursor, ISearchPredicate searchPred) throws HyracksDataException,
                 TreeIndexException {
@@ -1099,10 +1104,10 @@
         }
 
         @Override
-		public ITreeIndexCursor createDiskOrderScanCursor() {
-        	return new TreeDiskOrderScanCursor(leafFrameFactory.createFrame());
-		}
-        
+        public ITreeIndexCursor createDiskOrderScanCursor() {
+            return new TreeDiskOrderScanCursor(leafFrameFactory.createFrame());
+        }
+
         @Override
         public void diskOrderScan(ITreeIndexCursor cursor) throws HyracksDataException {
             ctx.reset(IndexOp.DISKORDERSCAN);
diff --git a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeSerachTest.java b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeSerachTest.java
index 6fe5ad3..48656ca 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeSerachTest.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeSerachTest.java
@@ -39,8 +39,8 @@
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMFileNameManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.BTreeFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMTreeFileNameManager;
-import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.BTreeFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTree;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTreeInMemoryFreePageManager;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTreeSearchCursor;
@@ -53,7 +53,7 @@
 
 public class LSMRTreeSerachTest extends AbstractLSMRTreeTest {
 
-    // create LSM-RTree of two dimensions
+    // create LSMRTree of two dimensions
     // fill the tree with random values using insertions
     // and then perform range search
     @Test
diff --git a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeTest.java b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeTest.java
index 867efcc..5b6f416 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeTest.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/LSMRTreeTest.java
@@ -48,8 +48,8 @@
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMFileNameManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.BTreeFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMTreeFileNameManager;
-import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.BTreeFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTree;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTreeInMemoryFreePageManager;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.RTreeFactory;
@@ -60,7 +60,7 @@
 
 public class LSMRTreeTest extends AbstractLSMRTreeTest {
 
-    // create an LSM-RTree of two dimensions
+    // create an LSMRTree of two dimensions
     // fill the tree with random values using insertions
     @Test
     public void test01() throws Exception {
@@ -208,9 +208,9 @@
 
     }
 
-    // create an LSM-RTree of two dimensions
+    // create an LSMRTree of two dimensions
     // fill the tree with random values using insertions
-    // and then delete all the tuples which result of an empty LSM-RTree
+    // and then delete all the tuples which result of an empty LSMRTree
     @Test
     public void test02() throws Exception {
 
@@ -403,7 +403,7 @@
 
     }
 
-    // create an LSM-RTree of three dimensions
+    // create an LSMRTree of three dimensions
     // fill the tree with random values using insertions
     @Test
     public void test03() throws Exception {
@@ -563,7 +563,7 @@
 
     }
 
-    // create an LSM-RTree of two dimensions
+    // create an LSMRTree of two dimensions
     // fill the tree with random integer key values using insertions
     @Test
     public void test04() throws Exception {