SQLite plugin doesn't work when I restart the app

I made an android app with ionic/cordova/sqlite plugin .When I launched the app, the db plugin works well, it open the database and execute sql query as expected. Next I use back button to exit the app and launch it again, I found the db is opened again but I can't execute query with this db, and I can't get the error message. I don't know why. If I remove this app from memory by menu button and launch app again, it works.

The android is 4.2.2. Could anyone know how I could fix it?

my db service:

angular.module('starter.controllers', ['ionic', 'ngCordova'])
.factory( '$h5_dbservice',
          [ '$cordovaSQLite','$rootScope',
            function( $cordovaSQLite,$rootScope ){
                return {
                    initDB : function() {
                        db = $cordovaSQLite.openDB( "h5app.db", 1 );
                        db.transaction(
                            function(tx) {
                                tx.executeSql('CREATE TABLE IF NOT EXISTS tab1  ( ... )'
                                tx.executeSql('CREATE TABLE IF NOT EXISTS tab2 ( ... )'
                                tx.executeSql('SELECT count(*) AS cnt FROM  tab1 WHERE ...

In my app.js

.run(function($ionicPlatform, $h5_dbservice) {
  $ionicPlatform.ready(function() {
    // Hide the accessory bar by default (remove this to show the accessory bar above the keyboard
    // for form inputs)
    if(window.cordova && window.cordova.plugins.Keyboard) {
      cordova.plugins.Keyboard.hideKeyboardAccessoryBar(true);
    }
    if(window.StatusBar) {
      // org.apache.cordova.statusbar required
      StatusBar.styleDefault();
    }
    $h5_dbservice.initDB();
  });