diff --git a/src/org/zoodb/internal/DataDeSerializerNoClass.java b/src/org/zoodb/internal/DataDeSerializerNoClass.java
index d0e8933d..4255d90f 100644
--- a/src/org/zoodb/internal/DataDeSerializerNoClass.java
+++ b/src/org/zoodb/internal/DataDeSerializerNoClass.java
@@ -65,7 +65,6 @@ private int readHeader(ZooClassDef clsDef, boolean allowSchemaMismatch) {
         //read class info:
     	clsOid = in.getHeaderClassOID();
     	if (!allowSchemaMismatch && clsOid != clsDef.getOid()) {
-    		System.err.println();
     		throw new UnsupportedOperationException("Schema evolution not yet supported: " + 
     				clsDef.getClassName() + ": " + Util.oidToString(clsDef.getOid()) + " to " + 
     				Util.oidToString(clsOid));
@@ -79,6 +78,13 @@ private int readHeader(ZooClassDef clsDef, boolean allowSchemaMismatch) {
         //instantiated object, only pages or possibly byte arrays.
     }
     
+    public static long getClassOid(StorageChannelInput in) {
+    	//skip OID
+    	in.readLong();
+        //read class info:
+    	return in.getHeaderClassOID();
+    }
+    
     public long getClassOid() {
     	//readHeader(clsDef)
         //Read OID
diff --git a/src/org/zoodb/internal/SerialInput.java b/src/org/zoodb/internal/SerialInput.java
index 84804ed2..9b8d1b22 100644
--- a/src/org/zoodb/internal/SerialInput.java
+++ b/src/org/zoodb/internal/SerialInput.java
@@ -57,14 +57,6 @@ public interface SerialInput {
 
 	public void skipRead(int nBytes);
 
-//	/**
-//	 * Assumes autopaging=true.
-//	 * @param pos
-//	 */
-//	public void seekPosAP(DATA_TYPE type, long pos);
-//
-//	public void seekPage(DATA_TYPE type, int page, int offs);
-
     public long getHeaderClassOID();
 
 	public long getHeaderTimestamp();
diff --git a/src/org/zoodb/internal/ZooClassDef.java b/src/org/zoodb/internal/ZooClassDef.java
index 622f4372..e9e41e82 100644
--- a/src/org/zoodb/internal/ZooClassDef.java
+++ b/src/org/zoodb/internal/ZooClassDef.java
@@ -545,7 +545,7 @@ public void associateSuperDef(ZooClassDef superDef) {
 	}
 
 	public void associateFields() {
-		ArrayList<ZooFieldDef> allFields = new ArrayList<ZooFieldDef>();
+		ArrayList<ZooFieldDef> allFields = new ArrayList<>();
 		
 		//For PersistenceCapableImpl _super may be null:
 		ZooClassDef sup = superDef;
@@ -582,7 +582,7 @@ public ZooFieldDef getField(String attrName) {
 
 	public Map<String, ZooFieldDef> getAllFieldsAsMap() {
 		if (fieldBuffer == null) {
-			fieldBuffer = new HashMap<String, ZooFieldDef>();
+			fieldBuffer = new HashMap<>();
 			for (ZooFieldDef def: getAllFields()) {
 				fieldBuffer.put(def.getName(), def);
 			}
diff --git a/src/org/zoodb/internal/ZooFieldDef.java b/src/org/zoodb/internal/ZooFieldDef.java
index 1499a1cb..647a4b1a 100644
--- a/src/org/zoodb/internal/ZooFieldDef.java
+++ b/src/org/zoodb/internal/ZooFieldDef.java
@@ -33,9 +33,11 @@
 
 public class ZooFieldDef {
 
-	public static final int OFS_INIITIAL = 8; //OID
+	public static final int BYTES_OF_OID = 8; //length of OID
+	public static final int BYTES_OF_SCHEMA_OID = 8; //lengths of Schema-OID
+	public static final int OFS_INIITIAL = BYTES_OF_OID + BYTES_OF_SCHEMA_OID; //OID + Schema-OID
 	
-	public static enum JdoType {
+	public enum JdoType {
 		PRIMITIVE(-1, true),
 		//Numbers are like SCOs. They cannot be indexable, because they can be 'null'!
 		//Furthermore, if the type is Number, then it could be everything from boolean to double.
diff --git a/src/org/zoodb/internal/server/DiskAccessOneFile.java b/src/org/zoodb/internal/server/DiskAccessOneFile.java
index d732d7e0..f83500e5 100644
--- a/src/org/zoodb/internal/server/DiskAccessOneFile.java
+++ b/src/org/zoodb/internal/server/DiskAccessOneFile.java
@@ -663,9 +663,8 @@ public long getObjectClass(long oid) {
 		}
 		
 		try {
-			//TODO use ObjectReader!?!?!
 			fileInAP.seekPage(PAGE_TYPE.DATA, oie.getPage(), oie.getOffs());
-			return new DataDeSerializerNoClass(fileInAP).getClassOid();
+			return DataDeSerializerNoClass.getClassOid(fileInAP);
 		} catch (Exception e) {
 			throw DBLogger.newObjectNotFoundException(
 					"ERROR reading object: " + Util.oidToString(oid));
diff --git a/src/org/zoodb/internal/server/StorageChannel.java b/src/org/zoodb/internal/server/StorageChannel.java
index 958aff24..326dd364 100644
--- a/src/org/zoodb/internal/server/StorageChannel.java
+++ b/src/org/zoodb/internal/server/StorageChannel.java
@@ -36,8 +36,6 @@ public interface StorageChannel {
 
 	void close();
 
-	void flush();
-
 	void write(ByteBuffer buf, long currentPage);
 
 	void readPage(ByteBuffer buf, long pageId);
diff --git a/src/org/zoodb/jdo/impl/QueryImpl.java b/src/org/zoodb/jdo/impl/QueryImpl.java
index 8db0cfe3..6b988305 100644
--- a/src/org/zoodb/jdo/impl/QueryImpl.java
+++ b/src/org/zoodb/jdo/impl/QueryImpl.java
@@ -517,7 +517,7 @@ private void applyQueryOnExtent(List<Object> ret, QueryAdvice qa) {
 				}
 			}
 		} else {
-			DBLogger.LOGGER.warn("query.execute() uses extent without index");
+			DBLogger.LOGGER.warn("query.execute() found no index to use");
 			if (DBStatistics.isEnabled()) {
 				pm.getSession().statsInc(STATS.QU_EXECUTED_WITHOUT_INDEX);
 				if (!ordering.isEmpty()) {