diff --git a/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContext.java b/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContext.java
index 7463d1c..18a81e5 100644
--- a/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContext.java
+++ b/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContext.java
@@ -15,6 +15,7 @@
 package edu.uci.ics.asterix.api.common;
 
 import java.io.IOException;
+import java.util.List;
 import java.util.logging.Logger;
 
 import edu.uci.ics.asterix.common.api.IAsterixAppRuntimeContext;
@@ -213,8 +214,8 @@
     }
 
     @Override
-    public IVirtualBufferCache getVirtualBufferCache(int datasetID) {
-        return indexLifecycleManager.getVirtualBufferCache(datasetID);
+    public List<IVirtualBufferCache> getVirtualBufferCaches(int datasetID) {
+        return indexLifecycleManager.getVirtualBufferCaches(datasetID);
     }
 
     @Override
diff --git a/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContextProviderForRecovery.java b/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContextProviderForRecovery.java
index 712d993..439feff 100644
--- a/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContextProviderForRecovery.java
+++ b/asterix-app/src/main/java/edu/uci/ics/asterix/api/common/AsterixAppRuntimeContextProviderForRecovery.java
@@ -14,6 +14,8 @@
  */
 package edu.uci.ics.asterix.api.common;
 
+import java.util.List;
+
 import edu.uci.ics.asterix.common.transactions.IAsterixAppRuntimeContextProvider;
 import edu.uci.ics.asterix.common.transactions.ITransactionSubsystem;
 import edu.uci.ics.asterix.transaction.management.service.transaction.AsterixRuntimeComponentsProvider;
@@ -88,8 +90,8 @@
     }
 
     @Override
-    public IVirtualBufferCache getVirtualBufferCache(int datasetID) {
-        return asterixAppRuntimeContext.getVirtualBufferCache(datasetID);
+    public List<IVirtualBufferCache> getVirtualBufferCaches(int datasetID) {
+        return asterixAppRuntimeContext.getVirtualBufferCaches(datasetID);
     }
 
     @Override
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/api/IAsterixAppRuntimeContext.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/api/IAsterixAppRuntimeContext.java
index d035303..4287212 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/api/IAsterixAppRuntimeContext.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/api/IAsterixAppRuntimeContext.java
@@ -15,6 +15,7 @@
 package edu.uci.ics.asterix.common.api;
 
 import java.io.IOException;
+import java.util.List;
 
 import edu.uci.ics.asterix.common.exceptions.ACIDException;
 import edu.uci.ics.asterix.common.exceptions.AsterixException;
@@ -62,5 +63,5 @@
 
     public double getBloomFilterFalsePositiveRate();
 
-    public IVirtualBufferCache getVirtualBufferCache(int datasetID);
+    public List<IVirtualBufferCache> getVirtualBufferCaches(int datasetID);
 }
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/AsterixVirtualBufferCacheProvider.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/AsterixVirtualBufferCacheProvider.java
index bd2828d..9efc9fd 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/AsterixVirtualBufferCacheProvider.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/AsterixVirtualBufferCacheProvider.java
@@ -14,6 +14,8 @@
  */
 package edu.uci.ics.asterix.common.context;
 
+import java.util.List;
+
 import edu.uci.ics.asterix.common.api.IAsterixAppRuntimeContext;
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.IVirtualBufferCache;
@@ -29,9 +31,9 @@
     }
 
     @Override
-    public IVirtualBufferCache getVirtualBufferCache(IHyracksTaskContext ctx) {
+    public List<IVirtualBufferCache> getVirtualBufferCaches(IHyracksTaskContext ctx) {
         return ((IAsterixAppRuntimeContext) ctx.getJobletContext().getApplicationContext().getApplicationObject())
-                .getVirtualBufferCache(datasetID);
+                .getVirtualBufferCaches(datasetID);
     }
 
 }
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
index 97b9346..a4d4daa 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
@@ -42,18 +42,19 @@
 
 public class DatasetLifecycleManager implements IIndexLifecycleManager, ILifeCycleComponent {
     private final AsterixStorageProperties storageProperties;
-    private final Map<Integer, MultitenantVirtualBufferCache> datasetVirtualBufferCaches;
+    private final Map<Integer, List<IVirtualBufferCache>> datasetVirtualBufferCaches;
     private final Map<Integer, ILSMOperationTracker> datasetOpTrackers;
     private final Map<Integer, DatasetInfo> datasetInfos;
     private final ILocalResourceRepository resourceRepository;
     private final long capacity;
     private long used;
+    private final static int NUM_MUTABLE_BUFFERS = 2;
 
     public DatasetLifecycleManager(AsterixStorageProperties storageProperties,
             ILocalResourceRepository resourceRepository) {
         this.storageProperties = storageProperties;
         this.resourceRepository = resourceRepository;
-        datasetVirtualBufferCaches = new HashMap<Integer, MultitenantVirtualBufferCache>();
+        datasetVirtualBufferCaches = new HashMap<Integer, List<IVirtualBufferCache>>();
         datasetOpTrackers = new HashMap<Integer, ILSMOperationTracker>();
         datasetInfos = new HashMap<Integer, DatasetInfo>();
         capacity = storageProperties.getMemoryComponentGlobalBudget();
@@ -113,9 +114,11 @@
         }
 
         if (dsInfo.referenceCount == 0 && dsInfo.isOpen && dsInfo.indexes.isEmpty()) {
-            IVirtualBufferCache vbc = getVirtualBufferCache(did);
-            assert vbc != null;
-            used -= (vbc.getNumPages() * vbc.getPageSize());
+            List<IVirtualBufferCache> vbcs = getVirtualBufferCaches(did);
+            assert vbcs != null;
+            for (IVirtualBufferCache vbc : vbcs) {
+                used -= (vbc.getNumPages() * vbc.getPageSize());
+            }
             datasetInfos.remove(did);
         }
 
@@ -137,9 +140,12 @@
         }
 
         if (!dsInfo.isOpen) {
-            IVirtualBufferCache vbc = getVirtualBufferCache(did);
-            assert vbc != null;
-            long additionalSize = vbc.getNumPages() * vbc.getPageSize();
+            List<IVirtualBufferCache> vbcs = getVirtualBufferCaches(did);
+            assert vbcs != null;
+            long additionalSize = 0;
+            for (IVirtualBufferCache vbc : vbcs) {
+                additionalSize += vbc.getNumPages() * vbc.getPageSize();
+            }
             while (used + additionalSize > capacity) {
                 if (!evictCandidateDataset()) {
                     throw new HyracksDataException("Cannot activate index since memory budget would be exceeded.");
@@ -166,7 +172,7 @@
         Collections.sort(datasetInfosList);
         for (DatasetInfo dsInfo : datasetInfosList) {
             ILSMOperationTracker opTracker = datasetOpTrackers.get(dsInfo.datasetID);
-            if (opTracker != null && ((PrimaryIndexOperationTracker) opTracker).getNumActiveOperations() == 0
+            if (opTracker != null && ((PrimaryIndexOperationTracker) opTracker).isActiveDataset()
                     && dsInfo.referenceCount == 0 && dsInfo.isOpen) {
                 for (IndexInfo iInfo : dsInfo.indexes.values()) {
                     if (iInfo.isOpen) {
@@ -176,8 +182,10 @@
                     assert iInfo.referenceCount == 0;
                 }
 
-                IVirtualBufferCache vbc = getVirtualBufferCache(dsInfo.datasetID);
-                used -= vbc.getNumPages() * vbc.getPageSize();
+                List<IVirtualBufferCache> vbcs = getVirtualBufferCaches(dsInfo.datasetID);
+                for (IVirtualBufferCache vbc : vbcs) {
+                    used -= vbc.getNumPages() * vbc.getPageSize();
+                }
                 dsInfo.isOpen = false;
                 return true;
             }
@@ -213,15 +221,20 @@
         return openIndexes;
     }
 
-    public IVirtualBufferCache getVirtualBufferCache(int datasetID) {
+    public List<IVirtualBufferCache> getVirtualBufferCaches(int datasetID) {
         synchronized (datasetVirtualBufferCaches) {
-            MultitenantVirtualBufferCache vbc = datasetVirtualBufferCaches.get(datasetID);
-            if (vbc == null) {
-                vbc = new MultitenantVirtualBufferCache(new VirtualBufferCache(new HeapBufferAllocator(),
-                        storageProperties.getMemoryComponentPageSize(), storageProperties.getMemoryComponentNumPages()));
-                datasetVirtualBufferCaches.put(datasetID, vbc);
+            List<IVirtualBufferCache> vbcs = datasetVirtualBufferCaches.get(datasetID);
+            if (vbcs == null) {
+                vbcs = new ArrayList<IVirtualBufferCache>();
+                for (int i = 0; i < NUM_MUTABLE_BUFFERS; i++) {
+                    MultitenantVirtualBufferCache vbc = new MultitenantVirtualBufferCache(new VirtualBufferCache(
+                            new HeapBufferAllocator(), storageProperties.getMemoryComponentPageSize(),
+                            storageProperties.getMemoryComponentNumPages() / NUM_MUTABLE_BUFFERS));
+                    vbcs.add(vbc);
+                }
+                datasetVirtualBufferCaches.put(datasetID, vbcs);
             }
-            return vbc;
+            return vbcs;
         }
     }
 
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
index 3347fcc..ef8748d 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/PrimaryIndexOperationTracker.java
@@ -15,7 +15,9 @@
 
 package edu.uci.ics.asterix.common.context;
 
+import java.util.List;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
 import edu.uci.ics.hyracks.storage.am.common.api.IModificationOperationCallback;
@@ -30,27 +32,27 @@
 public class PrimaryIndexOperationTracker extends BaseOperationTracker {
 
     private final DatasetLifecycleManager datasetLifecycleManager;
-    private final IVirtualBufferCache datasetBufferCache;
+    private final List<IVirtualBufferCache> datasetBufferCaches;
     private final int datasetID;
     // Number of active operations on a ILSMIndex instance.
-    private int numActiveOperations;
+    private AtomicInteger[] numActiveOperations;
 
     public PrimaryIndexOperationTracker(DatasetLifecycleManager datasetLifecycleManager, int datasetID,
             ILSMIOOperationCallbackFactory ioOpCallbackFactory) {
         super(ioOpCallbackFactory);
         this.datasetLifecycleManager = datasetLifecycleManager;
-        this.numActiveOperations = 0;
         this.datasetID = datasetID;
-        datasetBufferCache = datasetLifecycleManager.getVirtualBufferCache(datasetID);
+        this.datasetBufferCaches = datasetLifecycleManager.getVirtualBufferCaches(datasetID);
+        this.numActiveOperations = new AtomicInteger[datasetBufferCaches.size()];
+        for (int i = 0; i < numActiveOperations.length; i++) {
+            this.numActiveOperations[i] = new AtomicInteger(0);
+        }
     }
 
     @Override
-    public synchronized void beforeOperation(ILSMIndex index, LSMOperationType opType,
-            ISearchOperationCallback searchCallback, IModificationOperationCallback modificationCallback)
-            throws HyracksDataException {
-        if (opType == LSMOperationType.MODIFICATION || opType == LSMOperationType.FORCE_MODIFICATION) {
-            numActiveOperations++;
-        }
+    public void beforeOperation(ILSMIndex index, LSMOperationType opType, ISearchOperationCallback searchCallback,
+            IModificationOperationCallback modificationCallback) throws HyracksDataException {
+        numActiveOperations[index.getCurrentMutableComponentId()].incrementAndGet();
     }
 
     @Override
@@ -66,26 +68,16 @@
     @Override
     public void completeOperation(ILSMIndex index, LSMOperationType opType, ISearchOperationCallback searchCallback,
             IModificationOperationCallback modificationCallback) throws HyracksDataException {
-        int nActiveOps;
-        synchronized (this) {
-            if (opType == LSMOperationType.MODIFICATION || opType == LSMOperationType.FORCE_MODIFICATION) {
-                numActiveOperations--;
-            }
-            nActiveOps = numActiveOperations;
-        }
+        int nActiveOps = numActiveOperations[index.getCurrentMutableComponentId()].decrementAndGet();
+
         if (opType != LSMOperationType.FLUSH) {
             flushIfFull(nActiveOps);
         }
     }
 
-    private void flushIfFull(int nActiveOps) throws HyracksDataException {
+    private void flushIfFull(int componentId, int nActiveOps) throws HyracksDataException {
         // If we need a flush, and this is the last completing operation, then schedule the flush.
-        if (datasetBufferCache.isFull() && nActiveOps == 0) {
-            synchronized (this) {
-                if (numActiveOperations > 0) {
-                    return;
-                }
-            }
+        if (datasetBufferCaches.get(componentId).isFull() && nActiveOps == 0) {
             Set<ILSMIndex> indexes = datasetLifecycleManager.getDatasetIndexes(datasetID);
             for (ILSMIndex lsmIndex : indexes) {
                 ILSMIndexAccessor accessor = (ILSMIndexAccessor) lsmIndex.createAccessor(
@@ -97,13 +89,18 @@
     }
 
     public void exclusiveJobCommitted() throws HyracksDataException {
-        synchronized (this) {
-            numActiveOperations = 0;
+        for (int i = 0; i < numActiveOperations.length; i++) {
+            numActiveOperations[i].set(0);
+            flushIfFull(i, 0);
         }
-        flushIfFull(0);
     }
 
-    public synchronized int getNumActiveOperations() {
-        return numActiveOperations;
+    public boolean isActiveDataset() {
+        for (int i = 0; i < numActiveOperations.length; i++) {
+            if (numActiveOperations[i].get() > 0) {
+                return false;
+            }
+        }
+        return true;
     }
 }
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/transactions/IAsterixAppRuntimeContextProvider.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/transactions/IAsterixAppRuntimeContextProvider.java
index 05ac025..2f522b9 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/transactions/IAsterixAppRuntimeContextProvider.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/transactions/IAsterixAppRuntimeContextProvider.java
@@ -14,6 +14,8 @@
  */
 package edu.uci.ics.asterix.common.transactions;
 
+import java.util.List;
+
 import edu.uci.ics.hyracks.api.io.IIOManager;
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexLifecycleManager;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationCallbackProvider;
@@ -58,5 +60,5 @@
 
     public IIOManager getIOManager();
 
-    public IVirtualBufferCache getVirtualBufferCache(int datasetID);
+    public List<IVirtualBufferCache> getVirtualBufferCaches(int datasetID);
 }
diff --git a/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/bootstrap/MetadataBootstrap.java b/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/bootstrap/MetadataBootstrap.java
index aa976f8..82fee45 100644
--- a/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/bootstrap/MetadataBootstrap.java
+++ b/asterix-metadata/src/main/java/edu/uci/ics/asterix/metadata/bootstrap/MetadataBootstrap.java
@@ -333,7 +333,8 @@
                 + IndexFileNameUtil.prepareFileName(metadataStore + File.separator + index.getFileNameRelativePath(),
                         runtimeContext.getMetaDataIODeviceId());
         FileReference file = new FileReference(new File(filePath));
-        IVirtualBufferCache virtualBufferCache = runtimeContext.getVirtualBufferCache(index.getDatasetId().getId());
+        List<IVirtualBufferCache> virtualBufferCaches = runtimeContext.getVirtualBufferCaches(index.getDatasetId()
+                .getId());
         ITypeTraits[] typeTraits = index.getTypeTraits();
         IBinaryComparatorFactory[] comparatorFactories = index.getKeyBinaryComparatorFactory();
         int[] bloomFilterKeyFields = index.getBloomFilterKeyFields();
@@ -344,7 +345,7 @@
         ILSMOperationTracker opTracker = index.isPrimaryIndex() ? runtimeContext.getLSMBTreeOperationTracker(index
                 .getDatasetId().getId()) : new BaseOperationTracker(LSMBTreeIOOperationCallbackFactory.INSTANCE);
         if (create) {
-            lsmBtree = LSMBTreeUtils.createLSMTree(virtualBufferCache, file, bufferCache, fileMapProvider, typeTraits,
+            lsmBtree = LSMBTreeUtils.createLSMTree(virtualBufferCaches, file, bufferCache, fileMapProvider, typeTraits,
                     comparatorFactories, bloomFilterKeyFields, runtimeContext.getBloomFilterFalsePositiveRate(),
                     runtimeContext.getLSMMergePolicy(), opTracker, runtimeContext.getLSMIOScheduler(), rtcProvider);
             lsmBtree.create();
@@ -361,7 +362,7 @@
             resourceID = localResourceRepository.getResourceByName(file.getFile().getPath()).getResourceId();
             lsmBtree = (LSMBTree) indexLifecycleManager.getIndex(resourceID);
             if (lsmBtree == null) {
-                lsmBtree = LSMBTreeUtils.createLSMTree(virtualBufferCache, file, bufferCache, fileMapProvider,
+                lsmBtree = LSMBTreeUtils.createLSMTree(virtualBufferCaches, file, bufferCache, fileMapProvider,
                         typeTraits, comparatorFactories, bloomFilterKeyFields,
                         runtimeContext.getBloomFilterFalsePositiveRate(), runtimeContext.getLSMMergePolicy(),
                         opTracker, runtimeContext.getLSMIOScheduler(),
diff --git a/asterix-transactions/src/main/java/edu/uci/ics/asterix/transaction/management/resource/LSMBTreeLocalResourceMetadata.java b/asterix-transactions/src/main/java/edu/uci/ics/asterix/transaction/management/resource/LSMBTreeLocalResourceMetadata.java
index 8ce0174..cd894a1 100644
--- a/asterix-transactions/src/main/java/edu/uci/ics/asterix/transaction/management/resource/LSMBTreeLocalResourceMetadata.java
+++ b/asterix-transactions/src/main/java/edu/uci/ics/asterix/transaction/management/resource/LSMBTreeLocalResourceMetadata.java
@@ -15,6 +15,7 @@
 package edu.uci.ics.asterix.transaction.management.resource;
 
 import java.io.File;
+import java.util.List;
 
 import edu.uci.ics.asterix.common.context.BaseOperationTracker;
 import edu.uci.ics.asterix.common.ioopcallbacks.LSMBTreeIOOperationCallbackFactory;
@@ -49,8 +50,8 @@
     public ILSMIndex createIndexInstance(IAsterixAppRuntimeContextProvider runtimeContextProvider, String filePath,
             int partition) {
         FileReference file = new FileReference(new File(filePath));
-        IVirtualBufferCache virtualBufferCache = runtimeContextProvider.getVirtualBufferCache(datasetID);
-        LSMBTree lsmBTree = LSMBTreeUtils.createLSMTree(virtualBufferCache, file, runtimeContextProvider
+        List<IVirtualBufferCache> virtualBufferCaches = runtimeContextProvider.getVirtualBufferCaches(datasetID);
+        LSMBTree lsmBTree = LSMBTreeUtils.createLSMTree(virtualBufferCaches, file, runtimeContextProvider
                 .getBufferCache(), runtimeContextProvider.getFileMapManager(), typeTraits, cmpFactories,
                 bloomFilterKeyFields, runtimeContextProvider.getBloomFilterFalsePositiveRate(), runtimeContextProvider
                         .getLSMMergePolicy(), isPrimary ? runtimeContextProvider.getLSMBTreeOperationTracker(datasetID)