diff --git a/src/opt/hdf5/include/h5_group.cc.h b/src/opt/hdf5/include/h5_group.cc.h
new file mode 100644
index 0000000..4cb1bea
--- /dev/null
+++ b/src/opt/hdf5/include/h5_group.cc.h
@@ -0,0 +1,29 @@
+
+#ifndef __cxz_h5_group_cc_h__
+#define __cxz_h5_group_cc_h__
+
+namespace CNORXZ
+{
+    namespace hdf5
+    {
+	template <typename T>
+	Group& Group::addData(const String& name, const ArrayBase<T>& data)
+	{
+	    CXZ_ASSERT(this->isOpen(), "tried to extend closed group");
+	    CXZ_ERROR("not implemented!!!");
+	    return *this;
+	}
+
+	template <typename... Ts>
+	Group& Group::addTable(const String& name, const ArrayBase<Tuple<Ts...>>& data,
+			       const RangePtr& fields)
+	{
+	    CXZ_ASSERT(this->isOpen(), "tried to extend closed group");
+	    
+	    return *this;
+	}
+
+    }
+}
+
+#endif
diff --git a/src/opt/hdf5/include/h5_group.h b/src/opt/hdf5/include/h5_group.h
index 0196028..79daeff 100644
--- a/src/opt/hdf5/include/h5_group.h
+++ b/src/opt/hdf5/include/h5_group.h
@@ -29,6 +29,10 @@ namespace CNORXZ
 
 	    template <typename T>
 	    Group& addData(const String& name, const ArrayBase<T>& data);
+
+	    template <typename... Ts>
+	    Group& addTable(const String& name, const ArrayBase<Tuple<Ts...>>& data,
+			    const RangePtr& fields);
 	    
 	protected:
 	    MArray<ContentPtr> mCont;
diff --git a/src/opt/hdf5/include/h5_table.cc.h b/src/opt/hdf5/include/h5_table.cc.h
index 784b886..7f82327 100644
--- a/src/opt/hdf5/include/h5_table.cc.h
+++ b/src/opt/hdf5/include/h5_table.cc.h
@@ -16,49 +16,54 @@ namespace CNORXZ
 	}
 
 	template <typename... Ts>
-	STabel<Ts...>::STabel(const String& name, const ContentBase* _parent) :
+	STabel<Ts...>::STabel(const String& name, const ContentBase* _parent, const RangePtr& fields) :
 	    Table(name, _parent)
 	{
-	    // checks..!!!!
+	    constexpr SizeT N = sizeof...(Ts);
+	    if(mFields == nullptr){
+		CXZ_ASSERT(fields != nullptr, "field names have to be initialized");
+		mFields = fields;
+	    }
+	    CXZ_ASSERT(mFields->size() == sizeof...(Ts), "expected tuple of size = " << mFields->size()
+		       << ", got: " << sizeof...(Ts));
+
+	    if(mRecords == nullptr) {
+		auto mOffsets = MArray<SizeT>( mFields, iter<0,N>
+		    ( [&](auto i) { return &std::get<i>(t) - &t; },
+		      [](const auto&... e) { return Vector<SizeT>({e...}); }) );
+		auto mSizes = MArray<SizeT>( mFields, iter<0,N>
+		    ( [&](auto i) { return sizeof(std::get<i>(t)); },
+		      [](const auto&... e) { return Vector<SizeT>({e...}); }) );
+		auto mTypes = MArray<hid_t>( mFields, iter<0,N>
+		    ( [&](auto i) { return getTypeId(std::get<i>(t)); },
+		      [](const auto&... e) { return Vector<hid_t>({e...}); }) );
+	    }
+	    else {
+		iter<0,N>( [&](auto i) { CXZ_ASSERT
+			    ( &std::get<i>(t) - &t == mOffsets.data()[i],
+			      "wrong offset for field " << i << ": " << &std::get<i>(t) - &t
+			      << " vs " << mOffsets.data()[i] ); }, NoF{} );
+		iter<0,N>( [&](auto i) { CXZ_ASSERT
+			    ( sizeof(std::get<i>(t)) == mSizes.data()[i],
+			      "wrong size for field " << i << ": " << sizeof(std::get<i>(t))
+			      << " vs " << mSizes.data()[i] ); }, NoF{} );
+		iter<0,N>( [&](auto i) { CXZ_ASSERT
+			    ( getTypeId(std::get<i>(t)) == mTypes.data()[i],
+			      "wrong type for field " << i << ": " << getTypeId(std::get<i>(t))
+			      << " vs " << mTypes.data()[i] ); }, NoF{} );
+	    }
 	}
 
 	template <typename... Ts>
 	STabel& STabel<Ts...>::appendRecord(const Tuple<Ts...>& t)
 	{
-	    if(not mCheckedFile){
-		this->open();
-	    }
-	    this->close(); // H5TB does not require an open dataset
-	    CXZ_ASSERT(mFields != nullptr,
-		       "field names have to be initialized before creating table");
-	    CXZ_ASSERT(mFields->size() == sizeof...(Ts),
-		       "expected tuple of size = " << mFields->size()
-		       << ", got: " << sizeof...(Ts));
-	    
 	    RangePtr appr = CRangeFactory(1).create();
-	    auto offsets = iter<0,sizeof...(Ts)>
-		( [&](auto i) { return &std::get<i>(t) - &t; },
-		  [](const auto&... e) { return Vector<SizeT>({e...}); });
-	    auto sizes = iter<0,sizeof...(Ts)>
-		( [&](auto i) { return sizeof(std::get<i>(t)); },
-		  [](const auto&... e) { return Vector<SizeT>({e...}); });
-	    auto types = iter<0,sizeof...(Ts)>
-		( [&](auto i) { return getTypeId(std::get<i>(t)); },
-		  [](const auto&... e) { return Vector<hid_t>({e...}); });
 	    if(mRecords == nullptr){
 		mRecords = appr;
-		mSizes = MArray<SizeT>(std::move(sizes));
-		mOffsets = MArray<SizeT>(std::move(offsets));
-		mTypes = MArray<hid_t>(std::move(types));
-		
-		    // init
 	    }
 	    else {
-		// check consistency
-
 		mRecords = mRecords->extend(appr);
 	    }
-	    // append
 	    H5TBappend_records(mParent->id(), mName, 1, sizeof(t),
 			       mOffsets.data(), mSizes.data(), &t);
 	    return *this;
diff --git a/src/opt/hdf5/include/h5_table.h b/src/opt/hdf5/include/h5_table.h
index 707a77c..e105974 100644
--- a/src/opt/hdf5/include/h5_table.h
+++ b/src/opt/hdf5/include/h5_table.h
@@ -22,12 +22,9 @@ namespace CNORXZ
 	    virtual String path() const override final;
 	    virtual String filename() const override final;
 
-	    Table& openDSet();
 	    Table& initFieldNames(const Vector<String>& fnames);
-	    
-	    template <class F>
-	    decltype(auto) iterRecords(F&& f) const;
-
+	    Table& appendRecord(SizeT n, const char* data);
+	    Table& readRecord(SizeT pos, SizeT n, char* data);
 
 	private:
 	    RangePtr mRecords;
@@ -35,7 +32,7 @@ namespace CNORXZ
 	    MArray<SizeT> mSizes;
 	    MArray<SizeT> mOffsets;
 	    MArray<hid_t> mTypes;
-	    hid_t mType;
+	    hid_t mType = 0;
 	    bool mCheckedFile = false;
 	};
 
@@ -44,11 +41,13 @@ namespace CNORXZ
 	{
 	public:
 	    DEFAULT_MEMBERS(STabel);
-	    STabel(const String& name, const ContentBase* _parent);
+	    STabel(const String& name, const ContentBase* _parent, const RangePtr& fields);
 
 	    Table& appendRecord(const Tuple<Ts...>& t);
 	    Table& appendRecord(const MArray<Tuple<Ts...>>& t);
 	    
+	    template <class F>
+	    decltype(auto) iterRecords(F&& f) const;
 	};
     }
 }
diff --git a/src/opt/hdf5/lib/h5_group.cc b/src/opt/hdf5/lib/h5_group.cc
index c01ac58..ec130e6 100644
--- a/src/opt/hdf5/lib/h5_group.cc
+++ b/src/opt/hdf5/lib/h5_group.cc
@@ -90,14 +90,6 @@ namespace CNORXZ
 	    return *this;
 	}
 
-	template <typename T>
-	Group& Group::addData(const String& name, const ArrayBase<T>& data)
-	{
-	    CXZ_ASSERT(this->isOpen(), "tried to extend closed group");
-	    CXZ_ERROR(name << data.size() << " NOT IMPLEMENTED!!!");
-	    return *this;
-	}
-	
 	struct InitContData
 	{
 	    const ContentBase* parent;
diff --git a/src/opt/hdf5/lib/h5_table.cc b/src/opt/hdf5/lib/h5_table.cc
index 045cfa7..c60262c 100644
--- a/src/opt/hdf5/lib/h5_table.cc
+++ b/src/opt/hdf5/lib/h5_table.cc
@@ -8,7 +8,38 @@ namespace CNORXZ
     {
 	Table::Table(const String& name, const ContentBase* _parent) :
 	    ContentBase(name, _parent)
-	{}
+	{
+	    if(H5Lexists_by_name(mParent->id(), mName.c_str(), H5P_DEFAULT)){
+		hsize_t nfields = 0;
+		hsize_t nrecords = 0;
+		H5TBget_table_info(mParent->id(), mName.c_str(), &nfields, &nrecords);
+		mRecords = CRangeFactory( nrecords ).create();
+		Vector<char*> fieldsptr(nfields);
+		Vector<SizeT> offsets(nfields);
+		Vector<SizeT> sizes(nfields);
+		SizeT typesize = 0;
+		H5TBget_field_info(mParent->id(), mName.c_str(), fieldsptr.data(), sizes.data(),
+				   offsets.data(), &typesize);
+		Vector<String> fields(nfields);
+		for(SizeT i = 0; i != nfields; ++i){
+		    fields[i] = fieldsptr[i];
+		}
+		mFields = URangeFactory<String>( std::move(fields) ).create();
+		mSizes = MArray<SizeT>(mFields, std::move(sizes));
+		mOffsets = MArray<SizeT>(mFields, std::move(offsets));
+		this->open();
+		const SizeT n = H5Tget_nmembers(mType);
+		CXZ_ASSERT(n == mFields->size(),
+			   "number of dataset members does not match number of fields: "
+			   << n << " vs " << mFields->size());
+		Vector<hid_t> types(n);
+		for(SizeT i = 0; i != n; ++i){
+		    types[i] = H5Tget_member_class( mType, i );
+		}
+		mTypes = MArray<hid_t>(mFields, std::move(types));
+		this->close();
+	    }
+	}
 
 	Table::~Table()
 	{
@@ -27,36 +58,10 @@ namespace CNORXZ
 	
 	Table& Table::open()
 	{
-	    if(H5Oexists_by_name(mParent->id(), mName.c_str(), H5P_DEFAULT)){
-		hsize_t nfields = 0;
-		hsize_t nrecords = 0;
-		H5TBget_table_info(mParent->id(), mName.c_str(), &nfields, &nrecords);
-		mRecords = CRangeFactory( nrecords ).create();
-		Vector<char*> fieldsptr(nfields);
-		Vector<SizeT> offsets(nfields);
-		Vector<SizeT> sizes(nfields);
-		SizeT typesize = 0;
-		H5TBget_field_info(mParent->id(), mName.c_str(), fieldsptr.data(), sizes.data(),
-				   offsets.data(), &typesize);
-		Vector<String> fields(nfields);
-		for(SizeT i = 0; i != nfields; ++i){
-		    fields[i] = fieldsptr[i];
-		}
-		mFields = URangeFactory<String>( std::move(fields) ).create();
-		mSizes = MArray<SizeT>(mFields, std::move(sizes));
-		mOffsets = MArray<SizeT>(mFields, std::move(offsets));
-		this->openDSet();
-		const SizeT n = H5Tget_nmembers(mType);
-		CXZ_ASSERT(n == mFields->size(),
-			   "number of dataset members does not match number of fields: "
-			   << n << " vs " << mFields->size());
-		Vector<hid_t> types(n);
-		for(SizeT i = 0; i != n; ++i){
-		    types[i] = H5Tget_member_class( mType, i );
-		}
-		mTypes = MArray<hid_t>(mFields, std::move(types));
+	    if(mId == 0){
+		mId = H5Dopen(mParent->id(), mName.c_str(), H5P_DEFAULT);
+		mType = H5Dget_type(mId);
 	    }
-	    mCheckedFile = true; // now an empty mRecords etc indicates that there is currently no table at the requested location
 	    return *this;
 	}
 	
@@ -79,15 +84,6 @@ namespace CNORXZ
 	    return mParent->filename();
 	}
 
-	Table& Table::openDSet()
-	{
-	    if(mId == 0){
-		mId = H5Dopen(mParent->id(), mName.c_str(), H5P_DEFAULT);
-		mType = H5Dget_type(mId);
-	    }
-	    return *this;
-	}
-
 	Table& Table::initFieldNames(const Vector<String>& fnames)
 	{
 	    CXZ_ASSERT(mFields == nullptr, "fields already initialized");