diff --git a/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/LimitedSizeBufferedData.java b/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/LimitedSizeBufferedData.java
index d48f273ab94c60b6948d114fe9613071e260397c..448c54b8471b1810c63b97cc792b246c4e2fe174 100644
--- a/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/LimitedSizeBufferedData.java
+++ b/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/LimitedSizeBufferedData.java
@@ -74,8 +74,12 @@ public class LimitedSizeBufferedData<STORAGE_DATA extends ComparableStorageData
 
     @Override
     public List<STORAGE_DATA> read() {
-        List<STORAGE_DATA> collection = new ArrayList<>();
-        data.values().forEach(e -> e.forEach(collection::add));
-        return collection;
+        try {
+            List<STORAGE_DATA> collection = new ArrayList<>();
+            data.values().forEach(collection::addAll);
+            return collection;
+        } finally {
+            data.clear();
+        }
     }
 }
diff --git a/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/MergableBufferedData.java b/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/MergableBufferedData.java
index 24b92c0d417c9128fbb98b1b1e9b56f742482e25..9413137a54ca0f37b5bae75a38881aee3eb8c9a7 100644
--- a/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/MergableBufferedData.java
+++ b/oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/data/MergableBufferedData.java
@@ -57,6 +57,10 @@ public class MergableBufferedData<METRICS extends Metrics> implements BufferedDa
 
     @Override
     public List<METRICS> read() {
-        return buffer.values().stream().collect(Collectors.toList());
+        try {
+            return buffer.values().stream().collect(Collectors.toList());
+        } finally {
+            buffer.clear();
+        }
     }
 }