diff --git a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/PartitionedWordInvertedIndexTest.java b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/PartitionedWordInvertedIndexTest.java
index f432c08..db3f615 100644
--- a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/PartitionedWordInvertedIndexTest.java
+++ b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/PartitionedWordInvertedIndexTest.java
@@ -27,8 +27,8 @@
 import edu.uci.ics.hyracks.dataflow.common.data.marshalling.ShortSerializerDeserializer;
 import edu.uci.ics.hyracks.dataflow.common.data.marshalling.UTF8StringSerializerDeserializer;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ConstantMergePolicyProvider;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.invertedindex.dataflow.PartitionedLSMInvertedIndexDataflowHelperFactory;
 
 public class PartitionedWordInvertedIndexTest extends AbstractfWordInvertedIndexTest {
@@ -51,8 +51,8 @@
                 PointableBinaryComparatorFactory.of(IntegerPointable.FACTORY) };
 
         invertedIndexDataflowHelperFactory = new PartitionedLSMInvertedIndexDataflowHelperFactory(
-                new ConstantMergePolicyProvider(ImmediateSchedulerProvider.INSTANCE, MERGE_THRESHOLD),
-                RefCountingOperationTrackerFactory.INSTANCE, ImmediateSchedulerProvider.INSTANCE);
+                new ConstantMergePolicyProvider(MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE,
+                SynchronousSchedulerProvider.INSTANCE);
     }
 
     @Override
diff --git a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/WordInvertedIndexTest.java b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/WordInvertedIndexTest.java
index a3c4e6c..4ac6892 100644
--- a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/WordInvertedIndexTest.java
+++ b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/invertedindex/WordInvertedIndexTest.java
@@ -25,8 +25,8 @@
 import edu.uci.ics.hyracks.dataflow.common.data.marshalling.IntegerSerializerDeserializer;
 import edu.uci.ics.hyracks.dataflow.common.data.marshalling.UTF8StringSerializerDeserializer;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ConstantMergePolicyProvider;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.invertedindex.dataflow.LSMInvertedIndexDataflowHelperFactory;
 
 public class WordInvertedIndexTest extends AbstractfWordInvertedIndexTest {
@@ -46,8 +46,7 @@
                 PointableBinaryComparatorFactory.of(IntegerPointable.FACTORY) };
 
         invertedIndexDataflowHelperFactory = new LSMInvertedIndexDataflowHelperFactory(new ConstantMergePolicyProvider(
-                ImmediateSchedulerProvider.INSTANCE, MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE,
-                ImmediateSchedulerProvider.INSTANCE);
+                MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE, SynchronousSchedulerProvider.INSTANCE);
     }
 
     @Override
diff --git a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/btree/LSMBTreeOperatorTestHelper.java b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/btree/LSMBTreeOperatorTestHelper.java
index eee0c5a..2be0e83 100644
--- a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/btree/LSMBTreeOperatorTestHelper.java
+++ b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/btree/LSMBTreeOperatorTestHelper.java
@@ -19,8 +19,8 @@
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.dataflow.LSMBTreeDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ConstantMergePolicyProvider;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousSchedulerProvider;
 import edu.uci.ics.hyracks.tests.am.common.LSMTreeOperatorTestHelper;
 
 public class LSMBTreeOperatorTestHelper extends LSMTreeOperatorTestHelper {
@@ -32,8 +32,8 @@
     }
 
     public IIndexDataflowHelperFactory createDataFlowHelperFactory() {
-        return new LSMBTreeDataflowHelperFactory(new ConstantMergePolicyProvider(ImmediateSchedulerProvider.INSTANCE,
-                MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE, ImmediateSchedulerProvider.INSTANCE);
+        return new LSMBTreeDataflowHelperFactory(new ConstantMergePolicyProvider(MERGE_THRESHOLD),
+                RefCountingOperationTrackerFactory.INSTANCE, SynchronousSchedulerProvider.INSTANCE);
     }
 
 }
diff --git a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeOperatorTestHelper.java b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeOperatorTestHelper.java
index 5d24e18..8c6c99f 100644
--- a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeOperatorTestHelper.java
+++ b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeOperatorTestHelper.java
@@ -21,8 +21,8 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IPrimitiveValueProviderFactory;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ConstantMergePolicyProvider;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.dataflow.LSMRTreeDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.rtree.frames.RTreePolicyType;
 import edu.uci.ics.hyracks.tests.am.common.LSMTreeOperatorTestHelper;
@@ -39,8 +39,8 @@
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             IBinaryComparatorFactory[] btreeComparatorFactories, ILinearizeComparatorFactory linearizerCmpFactory) {
         return new LSMRTreeDataflowHelperFactory(valueProviderFactories, rtreePolicyType, btreeComparatorFactories,
-                new ConstantMergePolicyProvider(ImmediateSchedulerProvider.INSTANCE, MERGE_THRESHOLD),
-                RefCountingOperationTrackerFactory.INSTANCE, ImmediateSchedulerProvider.INSTANCE, linearizerCmpFactory);
+                new ConstantMergePolicyProvider(MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE,
+                SynchronousSchedulerProvider.INSTANCE, linearizerCmpFactory);
     }
 
 }
diff --git a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesOperatorTestHelper.java b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesOperatorTestHelper.java
index c0e4b9b..46ff507 100644
--- a/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesOperatorTestHelper.java
+++ b/hyracks-examples/hyracks-integration-tests/src/test/java/edu/uci/ics/hyracks/tests/am/lsm/rtree/LSMRTreeWithAntiMatterTuplesOperatorTestHelper.java
@@ -21,8 +21,8 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IPrimitiveValueProviderFactory;
 import edu.uci.ics.hyracks.storage.am.common.dataflow.IIndexDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ConstantMergePolicyProvider;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.dataflow.LSMRTreeWithAntiMatterTuplesDataflowHelperFactory;
 import edu.uci.ics.hyracks.storage.am.rtree.frames.RTreePolicyType;
 import edu.uci.ics.hyracks.tests.am.common.LSMTreeOperatorTestHelper;
@@ -39,9 +39,9 @@
             IPrimitiveValueProviderFactory[] valueProviderFactories, RTreePolicyType rtreePolicyType,
             IBinaryComparatorFactory[] btreeComparatorFactories, ILinearizeComparatorFactory linearizerCmpFactory) {
         return new LSMRTreeWithAntiMatterTuplesDataflowHelperFactory(valueProviderFactories, rtreePolicyType,
-                btreeComparatorFactories, new ConstantMergePolicyProvider(ImmediateSchedulerProvider.INSTANCE,
-                        MERGE_THRESHOLD), RefCountingOperationTrackerFactory.INSTANCE,
-                ImmediateSchedulerProvider.INSTANCE, linearizerCmpFactory);
+                btreeComparatorFactories, new ConstantMergePolicyProvider(MERGE_THRESHOLD),
+                RefCountingOperationTrackerFactory.INSTANCE, SynchronousSchedulerProvider.INSTANCE,
+                linearizerCmpFactory);
     }
 
 }
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicy.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicy.java
index be7efc4..1c72abf 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicy.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicy.java
@@ -18,19 +18,15 @@
 import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.impls.NoOpOperationCallback;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndex;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIndexAccessor;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 
 public class ConstantMergePolicy implements ILSMMergePolicy {
 
-    private final ILSMIOOperationScheduler ioScheduler;
-
     private final int threshold;
 
-    public ConstantMergePolicy(ILSMIOOperationScheduler ioScheduler, int threshold) {
-        this.ioScheduler = ioScheduler;
+    public ConstantMergePolicy(int threshold) {
         this.threshold = threshold;
     }
 
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicyProvider.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicyProvider.java
index 1234137..b404c9b 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicyProvider.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ConstantMergePolicyProvider.java
@@ -1,7 +1,6 @@
 package edu.uci.ics.hyracks.storage.am.lsm.common.impls;
 
 import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
-import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMMergePolicyProvider;
 
@@ -9,18 +8,15 @@
 
     private static final long serialVersionUID = 1L;
 
-    private final ILSMIOOperationSchedulerProvider schedulerProvider;
-
     private final int threshold;
 
-    public ConstantMergePolicyProvider(ILSMIOOperationSchedulerProvider schedulerProvider, int threshold) {
-        this.schedulerProvider = schedulerProvider;
+    public ConstantMergePolicyProvider(int threshold) {
         this.threshold = threshold;
     }
 
     @Override
     public ILSMMergePolicy getMergePolicy(IHyracksTaskContext ctx) {
-        return new ConstantMergePolicy(schedulerProvider.getIOScheduler(ctx), threshold);
+        return new ConstantMergePolicy(threshold);
     }
 
 }
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
index 6a1727f..f4aa944 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMHarness.java
@@ -50,6 +50,7 @@
     private final Logger LOGGER = Logger.getLogger(LSMHarness.class.getName());
 
     private final ILSMIndexInternal lsmIndex;
+
     private final ILSMMergePolicy mergePolicy;
     private final ILSMOperationTracker opTracker;
     private final ILSMIOOperationScheduler ioScheduler;
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMMergeInProgressException.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMMergeInProgressException.java
deleted file mode 100644
index ee239d3..0000000
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/LSMMergeInProgressException.java
+++ /dev/null
@@ -1,32 +0,0 @@
-/*
- * Copyright 2009-2012 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 edu.uci.ics.hyracks.storage.am.common.api.TreeIndexException;
-
-public class LSMMergeInProgressException extends TreeIndexException {
-
-    private static final long serialVersionUID = 1L;
-
-    public LSMMergeInProgressException(Exception e) {
-        super(e);
-    }
-
-    public LSMMergeInProgressException(String message) {
-        super(message);
-    }
-
-}
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateScheduler.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousScheduler.java
similarity index 89%
rename from hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateScheduler.java
rename to hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousScheduler.java
index 03a41dc..9bbd394 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateScheduler.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousScheduler.java
@@ -5,7 +5,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperation;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 
-public enum ImmediateScheduler implements ILSMIOOperationScheduler {
+public enum SynchronousScheduler implements ILSMIOOperationScheduler {
     INSTANCE;
 
     @Override
diff --git a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateSchedulerProvider.java b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousSchedulerProvider.java
similarity index 75%
rename from hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateSchedulerProvider.java
rename to hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousSchedulerProvider.java
index 91c0a2d..72d9d1d 100644
--- a/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/ImmediateSchedulerProvider.java
+++ b/hyracks-storage-am-lsm-common/src/main/java/edu/uci/ics/hyracks/storage/am/lsm/common/impls/SynchronousSchedulerProvider.java
@@ -4,12 +4,12 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationSchedulerProvider;
 
-public enum ImmediateSchedulerProvider implements ILSMIOOperationSchedulerProvider {
+public enum SynchronousSchedulerProvider implements ILSMIOOperationSchedulerProvider {
     INSTANCE;
 
     @Override
     public ILSMIOOperationScheduler getIOScheduler(IHyracksTaskContext ctx) {
-        return ImmediateScheduler.INSTANCE;
+        return SynchronousScheduler.INSTANCE;
     }
 
 }
diff --git a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeTestWorker.java b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeTestWorker.java
index 2c22b3a..ef67cc3 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeTestWorker.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/multithread/LSMBTreeTestWorker.java
@@ -33,7 +33,6 @@
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.impls.LSMBTree;
 import edu.uci.ics.hyracks.storage.am.lsm.btree.impls.LSMBTree.LSMBTreeAccessor;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMMergeInProgressException;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoOpIOOperationCallback;
 
 public class LSMBTreeTestWorker extends AbstractIndexTestWorker {
@@ -107,16 +106,7 @@
                 break;
 
             case MERGE:
-                try {
-                    accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
-                } catch (LSMMergeInProgressException e) {
-                    // Ignore ongoing merges. Do an insert instead.
-                    try {
-                        accessor.insert(tuple);
-                    } catch (BTreeDuplicateKeyException e1) {
-                        // Ignore duplicate keys, since we get random tuples.
-                    }
-                }
+                accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
                 break;
 
             default:
diff --git a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/perf/LSMTreeRunner.java b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/perf/LSMTreeRunner.java
index 25a8c01..339d7dc 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/perf/LSMTreeRunner.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/perf/LSMTreeRunner.java
@@ -39,7 +39,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMIOOperationScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryBufferCache;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateScheduler;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.common.buffercache.HeapBufferAllocator;
@@ -92,7 +92,7 @@
                 inMemNumPages, new TransientFileMapManager());
         IInMemoryFreePageManager memFreePageManager = new InMemoryFreePageManager(inMemNumPages,
                 new LIFOMetaDataFrameFactory());
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         lsmtree = LSMBTreeUtils.createLSMTree(memBufferCache, memFreePageManager, ioManager, file, bufferCache, fmp,
                 typeTraits, cmpFactories, NoMergePolicy.INSTANCE, RefCountingOperationTrackerFactory.INSTANCE,
                 ioScheduler);
diff --git a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
index 1a075cb..1523846 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-btree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/btree/util/LSMBTreeTestHarness.java
@@ -38,7 +38,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryBufferCache;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.InMemoryFreePageManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateScheduler;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.common.buffercache.HeapBufferAllocator;
@@ -85,7 +85,7 @@
         this.memPageSize = AccessMethodTestsConfig.LSM_BTREE_MEM_PAGE_SIZE;
         this.memNumPages = AccessMethodTestsConfig.LSM_BTREE_MEM_NUM_PAGES;
         this.hyracksFrameSize = AccessMethodTestsConfig.LSM_BTREE_HYRACKS_FRAME_SIZE;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }
@@ -98,7 +98,7 @@
         this.memPageSize = memPageSize;
         this.memNumPages = memNumPages;
         this.hyracksFrameSize = hyracksFrameSize;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }
diff --git a/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java b/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
index fc6d58a..2a1b69c 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/common/LSMInvertedIndexTestHarness.java
@@ -36,7 +36,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.DualIndexInMemoryBufferCache;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.DualIndexInMemoryFreePageManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateScheduler;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.common.buffercache.HeapBufferAllocator;
@@ -81,7 +81,7 @@
         this.memPageSize = AccessMethodTestsConfig.LSM_INVINDEX_MEM_PAGE_SIZE;
         this.memNumPages = AccessMethodTestsConfig.LSM_INVINDEX_MEM_NUM_PAGES;
         this.hyracksFrameSize = AccessMethodTestsConfig.LSM_INVINDEX_HYRACKS_FRAME_SIZE;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }
@@ -94,7 +94,7 @@
         this.memPageSize = memPageSize;
         this.memNumPages = memNumPages;
         this.hyracksFrameSize = hyracksFrameSize;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }
diff --git a/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/multithread/LSMInvertedIndexTestWorker.java b/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/multithread/LSMInvertedIndexTestWorker.java
index 8f61449..d6bb3d3 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/multithread/LSMInvertedIndexTestWorker.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-invertedindex-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/invertedindex/multithread/LSMInvertedIndexTestWorker.java
@@ -30,7 +30,6 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IIndexCursor;
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.datagen.DataGenThread;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMMergeInProgressException;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoOpIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.invertedindex.api.IInvertedIndexSearchModifier;
 import edu.uci.ics.hyracks.storage.am.lsm.invertedindex.exceptions.OccurrenceThresholdPanicException;
@@ -110,11 +109,7 @@
             }
 
             case MERGE: {
-                try {
-                    accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
-                } catch (LSMMergeInProgressException e) {
-                    insert(accessor, tuple);
-                }
+                accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
                 break;
             }
 
diff --git a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeTestWorker.java b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeTestWorker.java
index c8f49ab..154756e 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeTestWorker.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeTestWorker.java
@@ -27,7 +27,6 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.datagen.DataGenThread;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMMergeInProgressException;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoOpIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTree;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTree.LSMRTreeAccessor;
@@ -73,13 +72,7 @@
                 break;
 
             case MERGE:
-                try {
-                    accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
-                } catch (LSMMergeInProgressException e) {
-                    // Ignore ongoing merges. Do an insert instead.
-                    rearrangeTuple(tuple, cmp);
-                    accessor.insert(rearrangedTuple);
-                }
+                accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
                 break;
 
             default:
diff --git a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesTestWorker.java b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesTestWorker.java
index 5f233fa..661138d 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesTestWorker.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/multithread/LSMRTreeWithAntiMatterTuplesTestWorker.java
@@ -24,7 +24,6 @@
 import edu.uci.ics.hyracks.storage.am.common.api.IndexException;
 import edu.uci.ics.hyracks.storage.am.common.datagen.DataGenThread;
 import edu.uci.ics.hyracks.storage.am.common.ophelpers.MultiComparator;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.LSMMergeInProgressException;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoOpIOOperationCallback;
 import edu.uci.ics.hyracks.storage.am.lsm.rtree.impls.LSMRTreeWithAntiMatterTuples.LSMRTreeWithAntiMatterTuplesAccessor;
 import edu.uci.ics.hyracks.storage.am.rtree.impls.SearchPredicate;
@@ -62,13 +61,7 @@
                 break;
 
             case MERGE:
-                try {
-                    accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
-                } catch (LSMMergeInProgressException e) {
-                    // Ignore ongoing merges. Do an insert instead.
-                    rearrangeTuple(tuple, cmp);
-                    accessor.insert(rearrangedTuple);
-                }
+                accessor.scheduleMerge(NoOpIOOperationCallback.INSTANCE);
                 break;
 
             default:
diff --git a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
index 44e3a40..0a443b3 100644
--- a/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
+++ b/hyracks-tests/hyracks-storage-am-lsm-rtree-test/src/test/java/edu/uci/ics/hyracks/storage/am/lsm/rtree/util/LSMRTreeTestHarness.java
@@ -37,7 +37,7 @@
 import edu.uci.ics.hyracks.storage.am.lsm.common.api.ILSMOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.DualIndexInMemoryBufferCache;
 import edu.uci.ics.hyracks.storage.am.lsm.common.freepage.DualIndexInMemoryFreePageManager;
-import edu.uci.ics.hyracks.storage.am.lsm.common.impls.ImmediateScheduler;
+import edu.uci.ics.hyracks.storage.am.lsm.common.impls.SynchronousScheduler;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.NoMergePolicy;
 import edu.uci.ics.hyracks.storage.am.lsm.common.impls.RefCountingOperationTrackerFactory;
 import edu.uci.ics.hyracks.storage.common.buffercache.HeapBufferAllocator;
@@ -81,7 +81,7 @@
         this.memPageSize = AccessMethodTestsConfig.LSM_RTREE_MEM_PAGE_SIZE;
         this.memNumPages = AccessMethodTestsConfig.LSM_RTREE_MEM_NUM_PAGES;
         this.hyracksFrameSize = AccessMethodTestsConfig.LSM_RTREE_HYRACKS_FRAME_SIZE;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }
@@ -94,7 +94,7 @@
         this.memPageSize = memPageSize;
         this.memNumPages = memNumPages;
         this.hyracksFrameSize = hyracksFrameSize;
-        this.ioScheduler = ImmediateScheduler.INSTANCE;
+        this.ioScheduler = SynchronousScheduler.INSTANCE;
         this.mergePolicy = NoMergePolicy.INSTANCE;
         this.opTrackerFactory = RefCountingOperationTrackerFactory.INSTANCE;
     }