diff --git a/numass-main/src/main/groovy/inr/numass/scripts/Underflow.groovy b/numass-main/src/main/groovy/inr/numass/scripts/Underflow.groovy
index fcbc1087..98797e7e 100644
--- a/numass-main/src/main/groovy/inr/numass/scripts/Underflow.groovy
+++ b/numass-main/src/main/groovy/inr/numass/scripts/Underflow.groovy
@@ -7,20 +7,29 @@
 package inr.numass.scripts
 
 import hep.dataforge.io.ColumnedDataWriter
+import hep.dataforge.storage.commons.StorageUtils
 import hep.dataforge.tables.Table
-import inr.numass.storage.NumassData
-import inr.numass.storage.NumassDataLoader
+import inr.numass.storage.NMPoint
+import inr.numass.storage.NumassDataUtils
+import inr.numass.storage.NumassStorage
 import inr.numass.utils.UnderflowCorrection
 
-//File dataDir = new File("D:\\Work\\Numass\\data\\2016_04\\T2_data\\Fill_2_2\\set_7_b2a3433e54010000")
-//File dataDir = new File("D:\\Work\\Numass\\data\\2016_04\\T2_data\\Fill_2_2\\set_6_e26d123e54010000")
 //File dataDir = new File("D:\\Work\\Numass\\data\\2016_10\\Fill_1\\set_28")
-File dataDir = new File("D:\\Work\\Numass\\data\\2016_10\\Fill_2_wide\\set_31")
-if(!dataDir.exists()){
-    println "dataDir directory does not exist"
-}
-NumassData data = NumassDataLoader.fromLocalDir(null, dataDir)
-//NumassData data = NMFile.readFile(new File("D:\\Work\\Numass\\sterilie2013-2014\\dat\\2013\\SCAN06.DAT" ))
+//File dataDir = new File("D:\\Work\\Numass\\data\\2016_10\\Fill_2_wide\\set_31")
+
+File rootDir = new File("D:\\Work\\Numass\\data\\2016_10\\Fill_2_wide")
+
+NumassStorage storage = NumassStorage.buildLocalNumassRoot(rootDir, true);
+
+Iterable<NMPoint> data = NumassDataUtils.sumSpectra(
+        StorageUtils.loaderStream(storage).map { it.value }.filter { it.name.matches("set_.{2,3}") }
+)
+
+//if(!dataDir.exists()){
+//    println "dataDir directory does not exist"
+//}
+//NumassData data = NumassDataLoader.fromLocalDir(null, dataDir)
+////NumassData data = NMFile.readFile(new File("D:\\Work\\Numass\\sterilie2013-2014\\dat\\2013\\SCAN06.DAT" ))
 
 Table t = new UnderflowCorrection().fitAllPoints(data, 400, 650, 3100, 20);
 ColumnedDataWriter.writeDataSet(System.out, t, "underflow parameters")
diff --git a/numass-main/src/main/java/inr/numass/actions/DebunchAction.java b/numass-main/src/main/java/inr/numass/actions/DebunchAction.java
index 9e6202ae..2893e2a8 100644
--- a/numass-main/src/main/java/inr/numass/actions/DebunchAction.java
+++ b/numass-main/src/main/java/inr/numass/actions/DebunchAction.java
@@ -49,8 +49,7 @@ public class DebunchAction extends OneToOneAction<RawNMFile, RawNMFile> {
         double framelength = meta.getDouble("framelength", 5);
         double maxCR = meta.getDouble("maxcr", 100d);
 
-        RawNMFile res = new RawNMFile(source.getName());
-        res.setHead(source.getHead());
+        RawNMFile res = new RawNMFile(source.getName(), source.getHead());
         source.getData().stream().map((point) -> {
             double cr = point.selectChanels(lower, upper).getCR();
             if (cr < maxCR) {
diff --git a/numass-main/src/main/java/inr/numass/actions/FindBorderAction.java b/numass-main/src/main/java/inr/numass/actions/FindBorderAction.java
index 4cfadb33..a62f9e6d 100644
--- a/numass-main/src/main/java/inr/numass/actions/FindBorderAction.java
+++ b/numass-main/src/main/java/inr/numass/actions/FindBorderAction.java
@@ -86,7 +86,7 @@ public class FindBorderAction extends OneToOneAction<NumassData, Table> {
     }
 
     private void fill(ListTable.Builder dataBuilder, NumassData file, int lower, int upper, NMPoint reference) {
-        for (NMPoint point : file.getNMPoints()) {
+        for (NMPoint point : file) {
             if ((reference != null) && (point.getUset() == reference.getUset())) {
                 continue;
             }
diff --git a/numass-main/src/main/java/inr/numass/actions/MergeDataAction.java b/numass-main/src/main/java/inr/numass/actions/MergeDataAction.java
index 3afba48b..3e760db8 100644
--- a/numass-main/src/main/java/inr/numass/actions/MergeDataAction.java
+++ b/numass-main/src/main/java/inr/numass/actions/MergeDataAction.java
@@ -47,7 +47,7 @@ public class MergeDataAction extends ManyToOneAction<Table, Table> {
         if (meta.hasValue("grouping.byValue")) {
             groups = super.buildGroups(context, input, actionMeta);
         } else {
-            groups = GroupBuilder.byValue(MERGE_NAME, meta.getString(MERGE_NAME, "merge")).group(input);
+            groups = GroupBuilder.byValue(MERGE_NAME, meta.getString(MERGE_NAME, input.getName())).group(input);
         }
         return groups;
     }
diff --git a/numass-main/src/main/java/inr/numass/actions/PrepareDataAction.java b/numass-main/src/main/java/inr/numass/actions/PrepareDataAction.java
index 15e494bc..f34279de 100644
--- a/numass-main/src/main/java/inr/numass/actions/PrepareDataAction.java
+++ b/numass-main/src/main/java/inr/numass/actions/PrepareDataAction.java
@@ -100,7 +100,7 @@ public class PrepareDataAction extends OneToOneAction<NumassData, Table> {
         }
 
         List<DataPoint> dataList = new ArrayList<>();
-        for (NMPoint point : dataFile.getNMPoints()) {
+        for (NMPoint point : dataFile) {
 
             long total = point.getEventsCount();
             double uset = utransform.apply(point.getUset());
diff --git a/numass-main/src/main/java/inr/numass/actions/SlicedData.java b/numass-main/src/main/java/inr/numass/actions/SlicedData.java
index ca23d05b..85dc5670 100644
--- a/numass-main/src/main/java/inr/numass/actions/SlicedData.java
+++ b/numass-main/src/main/java/inr/numass/actions/SlicedData.java
@@ -36,23 +36,21 @@ public class SlicedData extends SimplePointSource {
     //format = {U,username1,username2, ...}
     private static final String UNAME = "U";
 
-    
-    private static TableFormat prepateFormat(Map<String,Pair<Integer,Integer>> intervals){
-        ArrayList<String> names = new ArrayList<>(intervals.keySet());
-        names.add(0, TNAME);        
-        names.add(0, UNAME);
-        return TableFormat.forNames(names);
-    }
 
-    
-    
-    public SlicedData(NMFile file, Map<String,Pair<Integer,Integer>> intervals, boolean normalize) {
+    public SlicedData(NMFile file, Map<String, Pair<Integer, Integer>> intervals, boolean normalize) {
         super(prepateFormat(intervals));
         fill(file, intervals, normalize);
     }
+
+    private static TableFormat prepateFormat(Map<String,Pair<Integer,Integer>> intervals){
+        ArrayList<String> names = new ArrayList<>(intervals.keySet());
+        names.add(0, TNAME);
+        names.add(0, UNAME);
+        return TableFormat.forNames(names);
+    }
     
     private void fill(NMFile file, Map<String,Pair<Integer,Integer>> intervals, boolean normalize){
-        for (NMPoint point : file.getNMPoints()) {
+        for (NMPoint point : file) {
             
             //создаем основу для будущей точки
             HashMap<String,Value> map = new HashMap<>();
diff --git a/numass-main/src/main/java/inr/numass/utils/UnderflowCorrection.java b/numass-main/src/main/java/inr/numass/utils/UnderflowCorrection.java
index 76ab74a7..eb8f790d 100644
--- a/numass-main/src/main/java/inr/numass/utils/UnderflowCorrection.java
+++ b/numass-main/src/main/java/inr/numass/utils/UnderflowCorrection.java
@@ -10,7 +10,6 @@ import hep.dataforge.meta.Meta;
 import hep.dataforge.tables.ListTable;
 import hep.dataforge.tables.Table;
 import inr.numass.storage.NMPoint;
-import inr.numass.storage.NumassData;
 import inr.numass.storage.RawNMPoint;
 import org.apache.commons.math3.analysis.ParametricUnivariateFunction;
 import org.apache.commons.math3.exception.DimensionMismatchException;
@@ -51,18 +50,18 @@ public class UnderflowCorrection {
         }
     }
 
-    public Table fitAllPoints(NumassData data, int xLow, int xHigh, int binning) {
+    public Table fitAllPoints(Iterable<NMPoint> data, int xLow, int xHigh, int binning) {
         ListTable.Builder builder = new ListTable.Builder("U", "amp", "expConst");
-        for (NMPoint point : data.getNMPoints()) {
+        for (NMPoint point : data) {
             double[] fitRes = getUnderflowExpParameters(point, xLow, xHigh, binning);
             builder.row(point.getUset(), fitRes[0], fitRes[1]);
         }
         return builder.build();
     }
 
-    public Table fitAllPoints(NumassData data, int xLow, int xHigh, int upper, int binning) {
+    public Table fitAllPoints(Iterable<NMPoint> data, int xLow, int xHigh, int upper, int binning) {
         ListTable.Builder builder = new ListTable.Builder("U", "amp", "expConst", "correction");
-        for (NMPoint point : data.getNMPoints()) {
+        for (NMPoint point : data) {
             double norm = ((double) point.getCountInWindow(xLow, upper))/point.getLength();
             double[] fitRes = getUnderflowExpParameters(point, xLow, xHigh, binning);
             builder.row(point.getUset(), fitRes[0], fitRes[1], fitRes[0] * fitRes[1] * (Math.exp(xLow / fitRes[1]) - 1d) / norm + 1d);
diff --git a/numass-storage/src/main/java/inr/numass/storage/NMFile.java b/numass-storage/src/main/java/inr/numass/storage/NMFile.java
index a26b246f..5a7e5b60 100644
--- a/numass-storage/src/main/java/inr/numass/storage/NMFile.java
+++ b/numass-storage/src/main/java/inr/numass/storage/NMFile.java
@@ -17,17 +17,17 @@ package inr.numass.storage;
 
 import hep.dataforge.description.ValueDef;
 import hep.dataforge.meta.Meta;
-import hep.dataforge.meta.MetaBuilder;
 import hep.dataforge.names.NamedMetaHolder;
+
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Stream;
 
 /**
- *
  * Объект, содержащий только спектры, но не сами события
  *
  * @author Darksnake
@@ -35,51 +35,33 @@ import java.util.List;
 @ValueDef(name = "numass.path", info = "Path to this data file in numass repository.")
 @ValueDef(name = "numass.name", info = "The name of this data file.")
 public class NMFile extends NamedMetaHolder implements NumassData {
-    
-    public static NMFile readStream(InputStream is, String fname, Meta config) throws IOException{
-        return new NMFile(new NumassDataReader(is, fname, config).read());
-    }
-    
-    public static NMFile readFile(File file) throws IOException{
-        return new NMFile(new NumassDataReader(file).read());
-    }    
 
-    private final String head;
     private final List<NMPoint> points;
 
     public NMFile(RawNMFile file) {
         super(file.getName(), file.meta());
-        this.head = file.getHead();
         points = new ArrayList<>();
         for (RawNMPoint point : file.getData()) {
             points.add(new NMPoint(point));
         }
     }
 
+    public static NMFile readStream(InputStream is, String fname, Meta config) throws IOException {
+        return new NMFile(new NumassDataReader(is, fname, config).read());
+    }
+
+    public static NMFile readFile(File file) throws IOException {
+        return new NMFile(new NumassDataReader(file).read());
+    }
+
     @Override
     public String getDescription() {
         return "";
     }
 
-    /**
-     * @return the head
-     */
-    public String getHead() {
-        return head;
-    }
-
     @Override
-    public Meta meta() {
-        return new MetaBuilder("info").setValue("info", head);
-    }
-
-
-    /**
-     * @return the points
-     */
-    @Override
-    public List<NMPoint> getNMPoints() {
-        return points;
+    public Stream<NMPoint> stream() {
+        return points.stream();
     }
 
     @Override
diff --git a/numass-storage/src/main/java/inr/numass/storage/NumassData.java b/numass-storage/src/main/java/inr/numass/storage/NumassData.java
index 79bff076..d9a79ac1 100644
--- a/numass-storage/src/main/java/inr/numass/storage/NumassData.java
+++ b/numass-storage/src/main/java/inr/numass/storage/NumassData.java
@@ -11,21 +11,32 @@ import hep.dataforge.names.Named;
 import hep.dataforge.tables.Table;
 
 import java.time.Instant;
+import java.util.Iterator;
 import java.util.List;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
- *
  * @author <a href="mailto:altavir@gmail.com">Alexander Nozik</a>
  */
-public interface NumassData extends Named, Annotated {
+public interface NumassData extends Named, Annotated, Iterable<NMPoint> {
 
     String getDescription();
 
     @Override
     Meta meta();
 
-    List<NMPoint> getNMPoints();
+    Stream<NMPoint> stream();
+
+    @Override
+    default Iterator<NMPoint> iterator() {
+        return stream().iterator();
+    }
+
+    default List<NMPoint> getNMPoints() {
+        return stream().collect(Collectors.toList());
+    }
 
     boolean isEmpty();
 
@@ -42,7 +53,7 @@ public interface NumassData extends Named, Annotated {
      * @return
      */
     default NMPoint getByUset(double U) {
-        for (NMPoint point : getNMPoints()) {
+        for (NMPoint point : this) {
             if (point.getUset() == U) {
                 return point;
             }
@@ -57,7 +68,7 @@ public interface NumassData extends Named, Annotated {
      * @return
      */
     default NMPoint getByUread(double U) {
-        for (NMPoint point : getNMPoints()) {
+        for (NMPoint point : this) {
             if (point.getUread() == U) {
                 return point;
             }
diff --git a/numass-storage/src/main/java/inr/numass/storage/NumassDataLoader.java b/numass-storage/src/main/java/inr/numass/storage/NumassDataLoader.java
index fc519093..f617b419 100644
--- a/numass-storage/src/main/java/inr/numass/storage/NumassDataLoader.java
+++ b/numass-storage/src/main/java/inr/numass/storage/NumassDataLoader.java
@@ -44,6 +44,7 @@ import java.util.*;
 import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static inr.numass.storage.RawNMPoint.MAX_EVENTS_PER_POINT;
 import static org.apache.commons.vfs2.FileType.FOLDER;
@@ -303,8 +304,8 @@ public class NumassDataLoader extends AbstractLoader implements ObjectLoader<Env
     }
 
     @Override
-    public List<NMPoint> getNMPoints() {
-        return this.getPoints().stream().parallel().map(this::readPoint).collect(Collectors.toList());
+    public Stream<NMPoint> stream() {
+        return this.getPoints().stream().parallel().map(this::readPoint);
     }
 
     public List<NMPoint> getNMPoints(Function<RawNMPoint, NMPoint> transformation) {
@@ -397,8 +398,8 @@ public class NumassDataLoader extends AbstractLoader implements ObjectLoader<Env
             }
 
             @Override
-            public List<NMPoint> getNMPoints() {
-                return NumassDataLoader.this.getNMPoints(transform);
+            public Stream<NMPoint> stream() {
+                return NumassDataLoader.this.stream();
             }
 
             @Override
diff --git a/numass-storage/src/main/java/inr/numass/storage/NumassDataReader.java b/numass-storage/src/main/java/inr/numass/storage/NumassDataReader.java
index b2cc84ff..38abc704 100644
--- a/numass-storage/src/main/java/inr/numass/storage/NumassDataReader.java
+++ b/numass-storage/src/main/java/inr/numass/storage/NumassDataReader.java
@@ -127,11 +127,8 @@ public class NumassDataReader {
     }
 
     private RawNMFile readFile(String name) throws IOException {
-
-        RawNMFile file = new RawNMFile(name);
         String head = readHead();//2048
-        file.setHead(head.replaceAll("\u0000", ""));
-
+        RawNMFile file = new RawNMFile(name, head.replaceAll("\u0000", ""));
         LocalDateTime filedate = readDate(head);
 
         int lab = readByte();
diff --git a/numass-storage/src/main/java/inr/numass/storage/NumassDataUtils.java b/numass-storage/src/main/java/inr/numass/storage/NumassDataUtils.java
new file mode 100644
index 00000000..9de69124
--- /dev/null
+++ b/numass-storage/src/main/java/inr/numass/storage/NumassDataUtils.java
@@ -0,0 +1,43 @@
+package inr.numass.storage;
+
+import java.time.Instant;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/**
+ * Created by darksnake on 30-Jan-17.
+ */
+public class NumassDataUtils {
+
+    public static Iterable<NMPoint> sumSpectra(Stream<NumassData> spectra) {
+        Map<Double, NMPoint> map = new HashMap<>();
+        spectra.forEach(datum -> {
+            datum.forEach(point -> {
+                double uset = point.getUset();
+                if (map.containsKey(uset)) {
+                    map.put(uset, join(point, map.get(uset)));
+                } else {
+                    map.put(uset, point);
+                }
+            });
+        });
+        return map.values();
+    }
+
+    private static NMPoint join(NMPoint first, NMPoint second) {
+        if (first.getUset() != second.getUset()) {
+            throw new RuntimeException("Voltage mismatch");
+        }
+        int[] newArray = new int[first.getSpectrum().length];
+        Arrays.setAll(newArray, i -> first.getSpectrum()[i] + second.getSpectrum()[i]);
+        return new NMPoint(
+                first.getUset(),
+                first.getUread(),
+                Instant.EPOCH,
+                first.getLength() + second.getLength(),
+                newArray
+        );
+    }
+}
diff --git a/numass-storage/src/main/java/inr/numass/storage/NumassStorage.java b/numass-storage/src/main/java/inr/numass/storage/NumassStorage.java
index 6e5a2e66..502fc8b4 100644
--- a/numass-storage/src/main/java/inr/numass/storage/NumassStorage.java
+++ b/numass-storage/src/main/java/inr/numass/storage/NumassStorage.java
@@ -186,6 +186,7 @@ public class NumassStorage extends FileStorage {
      */
     @SuppressWarnings("unchecked")
     public void pushNumassData(String fileName, ByteBuffer data) throws StorageException {
+        //FIXME move zip to internal
         try {
             FileObject nmFile = getDataDir().resolveFile(fileName + NUMASS_ZIP_EXTENSION);
             if (!nmFile.exists()) {
diff --git a/numass-storage/src/main/java/inr/numass/storage/RawNMFile.java b/numass-storage/src/main/java/inr/numass/storage/RawNMFile.java
index 1119dad1..7bdf11f1 100644
--- a/numass-storage/src/main/java/inr/numass/storage/RawNMFile.java
+++ b/numass-storage/src/main/java/inr/numass/storage/RawNMFile.java
@@ -15,7 +15,11 @@
  */
 package inr.numass.storage;
 
+import hep.dataforge.description.ValueDef;
+import hep.dataforge.meta.Meta;
+import hep.dataforge.meta.MetaBuilder;
 import hep.dataforge.names.NamedMetaHolder;
+
 import java.io.BufferedOutputStream;
 import java.io.OutputStream;
 import java.io.PrintWriter;
@@ -24,29 +28,34 @@ import java.util.List;
 
 /**
  * Contains the whole data but requires a lot of memory
+ *
  * @author Darksnake
  */
+@ValueDef(name = "info", info = "file text header")
 public class RawNMFile extends NamedMetaHolder {
 
 //    public static String TYPE = ":data:numassdatafile";
 
-    private final List<RawNMPoint> points;
-    
-    private String head;
+    private final List<RawNMPoint> points = new ArrayList<>();
 
-    public void setHead(String head) {
-        this.head = head;
-    }
-
-    public String getHead() {
-        return head;
-    }
 
     public RawNMFile(String fileName) {
         super(fileName);
-        this.points = new ArrayList<>();
     }
 
+    public RawNMFile(String name, Meta meta) {
+        super(name, meta);
+    }
+
+    public RawNMFile(String name, String header) {
+        super(name, new MetaBuilder("meta").setValue("info", header));
+    }
+
+    public String getHead() {
+        return meta().getString("info", "");
+    }
+
+    @Deprecated
     public void generatePAW(OutputStream stream) {
         PrintWriter writer = new PrintWriter(new BufferedOutputStream(stream));
         long counter = 0;
@@ -63,8 +72,9 @@ public class RawNMFile extends NamedMetaHolder {
 
     /**
      * merge of all point with given Uset
+     *
      * @param U
-     * @return 
+     * @return
      */
     public RawNMPoint getByUset(double U) {
         RawNMPoint res = null;
@@ -80,18 +90,19 @@ public class RawNMFile extends NamedMetaHolder {
         }
         return res;
     }
-    
-    
+
+
     /**
      * merge of all point with given Uread
+     *
      * @param U
-     * @return 
+     * @return
      */
     public RawNMPoint getByUread(double U) {
         RawNMPoint res = null;
 
         for (RawNMPoint point : points) {
-            if (point.getUread()== U) {
+            if (point.getUread() == U) {
                 if (res == null) {
                     res = point.clone();
                 } else {
@@ -100,7 +111,7 @@ public class RawNMFile extends NamedMetaHolder {
             }
         }
         return res;
-    }    
+    }
 
     /**
      * @return the data