@Override
  public void toDelta(DataOutput out) throws IOException {
    out.writeInt(maxInactiveInterval);
    out.writeLong(lastAccessedTime);

    synchronized (deltas) {
      DataSerializer.writeInteger(deltas.size(), out);
      for (Map.Entry<String, DeltaEvent> e : deltas.entrySet()) {
        DataSerializer.writeString(e.getKey(), out);
        DataSerializer.writeObject(e.getValue(), out);
      }
      deltas.clear();
    }

    out.writeUTF(jvmOwnerId);
  }
This map holds the updates to attributes
extensions/geode-modules-session-internal/src/main/java/org/apache/geode/modules/session/internal/filter/attributes/AbstractDeltaSessionAttributes.java