BATCH api An error occurred. Fatal error : Out of memory

Question

I'm using batch API in a custom module to clone millions of nodes programmatically but I am facing an error:

An error occurred. /batch?id=7&op=do
Fatal error: Out of memory (allocated -1179648000) (tried to allocate 40961 bytes) in

I try to optimize my code using the varible $limit for processing by lot but it seem to be not work

For example I have 10 data in my database and I put $ limit = 5; and it recovers only 5 data

But according the document http://envisioninteractive.com/drupal/drupal-batch-api-in-a-nutshell/ the limit Set the number of nodes you want to create within a single iteration of the batch. This number should be pretty low as it is the reason why we're creating the batch process in the first place.

here is my code :

function mymodule_menu() {
      $items = array();
      $items['mymodule'] = array(
        'title' => t('Cloner une liste'),
        'page callback' => 'drupal_get_form',
        'page arguments' => array('mymodule_form'),
        'access arguments' => array('access content'),
        'type' => MENU_NORMAL_ITEM,
      );
      return $items;
}

function mymodule_form() {
      global $base_url;
      $return_url = $base_url .'/gestion_creche_liste/'.arg(1);
      $node_tmp = node_load(arg(1));
      $default = 'Clone de ' . $node_tmp->title;
      $form['title_liste'] = array(
        '#type' => 'textfield',
        '#title' => t('Title'),
        '#default_value' => $default,
        '#required' => TRUE,
      );
       $form['description_liste'] = array(
        '#type' => 'textarea',
        '#title' => t('Description'),
        '#required' => false,
      );
      $form['retour'] = array(
        '#type' => 'button',
        '#value' => t('Retour'),
        '#prefix' => '',
        '#attributes' => array('onClick' => "window.location.href='".$return_url."'; return true;"),
        '#post_render' => array('change_button_type'),
       );
      $form['submit'] = array(
        '#type' => 'submit',
        '#value' => t('Save')
      );
      return $form;
    }

function theme_questionnaire_etape_trois_formulaire($form){
      $output = '';
      $output .= '<p><label for="edit-title_liste_value"><span> Titre liste * : </span>';
      $output .= str_replace('div','t',drupal_render($form['title_liste']));
      $output .= '</label></p>';

      $output .= '<p><label for="edit-field_description_liste_value"><span>Description : </span>';
      $output .= str_replace('div','t',drupal_render($form['description_liste']));
      $output .= '</label></p>';

      $output .= '<div id="btn">';
      $output .= drupal_render($form['submit']);
      $output .= '</div>';
      $output .= drupal_render($form);
      return $output;
}     

function mymodule_form_submit($form, &$form_state) {    

    $batch = array(
        'operations' => array(
          array('batch_clonerliste_op',  array($form_state['values']['title_liste'],$form_state['values']['description_liste'])),
          array('batch_mymodule_op',  array(arg(1))),
          ),
        'finished' => 'batch_mymodule_finished',
        'title' => t('Processing Example Batch'),
        'init_message' => t('Clone is starting'),
        'progress_message' => t('Processed @current out of @total.'),
        'error_message' => t('Example Batch has encountered an error.'),
    );



     batch_set($batch);
}


function batch_clonerliste_op($options1,$options2,&$context) {
     if(!isset($context['sandbox']['progress'])) {
        $context['sandbox']['progress'] = 0;
        $context['sandbox']['max'] = 1;
      }
     $node_liste = new stdClass();
     $node_liste->type = 'liste';
     $node_liste->language = 'fr';
     $node_liste->title = $options1;
     $node_liste->field_description_liste[0]['value'] = $options2;
     node_save($node_liste);

     $context['results']['nid'] = $node_liste->nid;  
     $context['sandbox']['progress']++;
     $context['message'] = t('Now processing %node', array('%node' => $node_liste->title));        

     if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
            $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
     } 
}


function batch_mymodule_op($options3,&$context) {
     $nid_liste = $context['results']['nid'];
     $tmp = get_curent_creche_liste($options3);
     $total = $num_rows = db_result(
     db_query("SELECT COUNT(DISTINCT nid) FROM  {content_field_liste_creche} WHERE field_liste_creche_nid = '%s'",$options3)); 

     if (!isset($context['sandbox']['progress'])) {
        $context['sandbox']['progress'] = 0;
        $context['sandbox']['current_node'] = 0;
        $context['results'][] = 0;
        $context['sandbox']['max'] = $total;
      }

//in total i have 10 date inside my database for exemple and i set limit = 5 $limit = 5;

        $result = db_query_range("SELECT DISTINCT nid FROM {content_field_liste_creche}  where field_liste_creche_nid = %s and nid != %d", array($options3,$context['sandbox']['current_node']), 0, $limit);
  while ($row = db_fetch_array($result)) {
                   $node = node_load($row['nid'],NULL,TRUE);
                   $node->field_liste_creche[]['nid'] = $nid_liste;
                   $node = node_submit($node);
                   node_save($node);

                   $context['sandbox']['progress']++;
                   $context['results'][]++;
                   $context['sandbox']['current_node'] = $node->nid;
                   $context['message'] = t('Now processing %node', array('%node' => $node->title));        
          } 

     if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
            $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
     } 
}


function batch_mymodule_finished($success, $results, $operations) {
     if ($success) {
        $message = count($results)-2 .' processed.';
     }
     else {
        $error_operation = reset($operations);
        $message = 'An error occurred while processing ' . $error_operation[0] . ' with arguments :' . print_r($error_operation[0], TRUE);
     }
     drupal_set_message($message);
     drupal_set_message('Clone réussie');
     drupal_goto('gestion_liste');
}


function get_curent_creche_liste($nid_list){
      $nid_creche_list = array();
      $query = "SELECT DISTINCT nid FROM  content_field_liste_creche WHERE field_liste_creche_nid ='".$nid_list."'";
      $result = db_query($query);       
      while ($row =db_fetch_object($result)) {
         $nid_creche_list[] = $row->nid;
      }
      return $nid_creche_list;
}

thank you very much in advance for your help