diff --git a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
index 81901b1..46d18e2 100644
--- a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
+++ b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
@@ -28,10 +28,6 @@ public class PersistentMap<K, V> {
 		void visit(PersistentMapDiskNode node, PersistentMapDiskNode parentNode, NodeEntry nodeEntry, int depth);
 	}
 
-	interface NodeVisitorCallback {
-		void visit(PersistentMapDiskNode node, int depth);
-	}
-
 	public interface EncoderDecoder<O> {
 		public byte[] encode(O object);
 
@@ -309,24 +305,6 @@ public class PersistentMap<K, V> {
 		}
 	}
 
-	public void visitNodesPreOrder(final NodeVisitorCallback visitor) throws IOException {
-		final long rootNodeOffset = readNodeOffsetOfRootNode();
-		visitNodesPreOrderRecursively(rootNodeOffset, visitor, 0);
-	}
-
-	private void visitNodesPreOrderRecursively(final long nodeOffset, final NodeVisitorCallback visitor,
-			final int depth) throws IOException {
-		final PersistentMapDiskNode node = getNode(nodeOffset);
-
-		visitor.visit(node, depth);
-		for (final NodeEntry child : node.getEntries()) {
-			if (child.isInnerNode()) {
-				final long childNodeOffset = VariableByteEncoder.decodeFirstValue(child.getValue());
-				visitNodesPreOrderRecursively(childNodeOffset, visitor, depth + 1);
-			}
-		}
-	}
-
 	private long readNodeOffsetOfRootNode() throws IOException {
 		final DiskBlock diskBlock = diskStore.getDiskBlock(NODE_OFFSET_TO_ROOT_NODE, diskStore.minAllocationSize());