--- a/src/alice/datasegment/DataSegmentKey.java	Tue Feb 21 21:11:50 2012 +0900
+++ b/src/alice/datasegment/DataSegmentKey.java	Tue Feb 21 22:55:17 2012 +0900
@@ -2,7 +2,6 @@
 
 import java.util.ArrayList;
 import java.util.Iterator;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import alice.datasegment.Command; 
 
@@ -15,16 +14,16 @@
 	
 	private ArrayList<DataSegmentValue> dataList = new ArrayList<DataSegmentValue>();
 	private ArrayList<Command> waitList = new ArrayList<Command>();
-	private AtomicInteger tailIndex = new AtomicInteger(1);
+	private int tailIndex = 1;
 	
-	public void runCommand(Command cmd) {
+	public synchronized void runCommand(Command cmd) {
 		switch (cmd.type) {
 		case UPDATE:
 			if (dataList.size() != 0) {
 				dataList.remove(0);
 			}
 		case PUT:
-			int index = tailIndex.getAndIncrement();
+			int index = tailIndex++;
 			DataSegmentValue dsv = new DataSegmentValue(index, cmd.val, cmd.reverseKey); 
 			dataList.add(dsv);
 			// Process waiting peek and take commands
@@ -45,7 +44,7 @@
 			}
 			break;
 		case PEEK:
-			if (cmd.index >= tailIndex.get()) {
+			if (cmd.index >= tailIndex) {
 				waitList.add(cmd);
 				break;
 			}
@@ -65,7 +64,7 @@
 				waitList.add(cmd);
 			break;
 		case TAKE:
-			if (cmd.index >= tailIndex.get()) {
+			if (cmd.index >= tailIndex) {
 				waitList.add(cmd);
 				break;
 			}