diff --git a/source/de/anomic/kelondro/text/IODispatcher.java b/source/de/anomic/kelondro/text/IODispatcher.java
index ac2dfba96..9b8bc8c8f 100644
--- a/source/de/anomic/kelondro/text/IODispatcher.java
+++ b/source/de/anomic/kelondro/text/IODispatcher.java
@@ -27,6 +27,7 @@ package de.anomic.kelondro.text;
 import java.io.File;
 import java.io.IOException;
 import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.Semaphore;
 
 import de.anomic.kelondro.blob.BLOBArray;
 import de.anomic.kelondro.index.Row;
@@ -46,33 +47,29 @@ import de.anomic.kelondro.util.Log;
  */
 public class IODispatcher <ReferenceType extends Reference> extends Thread {
 
-    private final Boolean poison, vita;
-    private ArrayBlockingQueue<Boolean>  controlQueue;
+    private Semaphore                    controlQueue;
+    private Semaphore                    termination;
     private ArrayBlockingQueue<MergeJob> mergeQueue;
     private ArrayBlockingQueue<DumpJob>  dumpQueue;
-    private ArrayBlockingQueue<Boolean>  termQueue;
-    ReferenceFactory<ReferenceType> factory;
+    private ReferenceFactory<ReferenceType> factory;
+    private boolean                      terminate;
     
     public IODispatcher(ReferenceFactory<ReferenceType> factory, int dumpQueueLength, int mergeQueueLength) {
         this.factory = factory;
-        this.poison = new Boolean(false);
-        this.vita = new Boolean(true);
-        this.controlQueue = new ArrayBlockingQueue<Boolean>(dumpQueueLength + mergeQueueLength + 1);
+        this.termination = new Semaphore(0);
+        this.controlQueue = new Semaphore(0);
         this.dumpQueue = new ArrayBlockingQueue<DumpJob>(dumpQueueLength);
         this.mergeQueue = new ArrayBlockingQueue<MergeJob>(mergeQueueLength);
-        this.termQueue = new ArrayBlockingQueue<Boolean>(1);
+        this.terminate = false;
     }
     
     public synchronized void terminate() {
-        if (termQueue != null && controlQueue != null && this.isAlive()) {
-            try {
-                controlQueue.put(poison);
-            } catch (InterruptedException e) {
-                e.printStackTrace();
-            }
+        if (termination != null && controlQueue != null && this.isAlive()) {
+            this.terminate = true;
+            this.controlQueue.release();
             // await termination
             try {
-                termQueue.take();
+                termination.acquire();
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
@@ -81,12 +78,14 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
     
     public synchronized void dump(ReferenceContainerCache<ReferenceType> cache, File file, ReferenceContainerArray<ReferenceType> array) {
         if (dumpQueue == null || controlQueue == null || !this.isAlive()) {
+            Log.logWarning("IODispatcher", "emergency dump of file " + file.getName());
             cache.dump(file);
         } else {
             DumpJob job = new DumpJob(cache, file, array);
             try {
-                dumpQueue.put(job);
-                controlQueue.put(vita);
+                this.dumpQueue.put(job);
+                this.controlQueue.release();
+                Log.logInfo("IODispatcher", "appended dump job for file " + file.getName());
             } catch (InterruptedException e) {
                 e.printStackTrace();
                 cache.dump(file);
@@ -95,12 +94,13 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
     }
     
     public synchronized int queueLength() {
-        return (controlQueue == null) ? 0 : controlQueue.size();
+        return (controlQueue == null) ? 0 : controlQueue.availablePermits();
     }
     
     public synchronized void merge(File f1, File f2, BLOBArray array, Row payloadrow, File newFile) {
         if (mergeQueue == null || controlQueue == null || !this.isAlive()) {
             try {
+                Log.logWarning("IODispatcher", "emergency merge of files " + f1.getName() + ", " + f2.getName() + " to " + newFile.getName());
                 array.mergeMount(f1, f2, factory, payloadrow, newFile);
             } catch (IOException e) {
                 e.printStackTrace();
@@ -108,8 +108,9 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
         } else {
             MergeJob job = new MergeJob(f1, f2, array, payloadrow, newFile);
             try {
-                mergeQueue.put(job);
-                controlQueue.put(vita);
+                this.mergeQueue.put(job);
+                this.controlQueue.release();
+                Log.logInfo("IODispatcher", "appended merge job of files " + f1.getName() + ", " + f2.getName() + " to " + newFile.getName());
             } catch (InterruptedException e) {
                 e.printStackTrace();
                 try {
@@ -125,7 +126,9 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
         MergeJob mergeJob;
         DumpJob dumpJob;
         try {
-            loop: while (controlQueue.take() != poison) {
+            loop: while (true) {
+                controlQueue.acquire();
+                
                 // prefer dump actions to flush memory to disc
                 if (dumpQueue.size() > 0) {
                     try {
@@ -137,6 +140,7 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
                     }
                     continue loop;
                 }
+                
                 // otherwise do a merge operation
                 if (mergeQueue.size() > 0) {
                     try {
@@ -148,19 +152,26 @@ public class IODispatcher <ReferenceType extends Reference> extends Thread {
                     }
                     continue loop;
                 }
+                
+                // check termination
+                if (this.terminate) {
+                    Log.logInfo("IODispatcher", "catched termination signal");
+                    break;
+                }
+
+                Log.logSevere("IODispatcher", "main loop in bad state, dumpQueue.size() = " + dumpQueue.size() + ", mergeQueue.size() = " + mergeQueue.size() + ", controlQueue.availablePermits() = " + controlQueue.availablePermits());
                 assert false; // this should never happen
             }
+            Log.logInfo("IODispatcher", "loop terminated");
         } catch (InterruptedException e) {
             e.printStackTrace();
             Log.logSevere("IODispatcher", "main run job was interrupted (3)", e);
         } finally {
             Log.logInfo("IODispatcher", "terminating run job");
             controlQueue = null;
-            try {
-                termQueue.put(poison);
-            } catch (InterruptedException e) {
-                e.printStackTrace();
-            }
+            dumpQueue = null;
+            mergeQueue = null;
+            termination.release();
         }
     }