diff --git a/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/elasticsearch/BulkUpload.java b/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/elasticsearch/BulkUpload.java
index 9c69ea2..4ad2926 100644
--- a/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/elasticsearch/BulkUpload.java
+++ b/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/elasticsearch/BulkUpload.java
@@ -125,6 +125,7 @@ public class BulkUpload {
                 request.add(new IndexRequest(elasticSearchIndexName).id(idES)
                         .source(ace.toJson(),XContentType.JSON));
 
+                log.info("Indexing: "+idES+" :: "+ace.toJson());
                 BulkResponse bulkResponse = client.bulk(request, RequestOptions.DEFAULT);
                 if (bulkResponse!=null) {
                     esResponseCode = bulkResponse.status().getStatus();
@@ -133,6 +134,9 @@ public class BulkUpload {
                         log.error("FailureMessage: " + bulkResponse.buildFailureMessage());
                     }
                 }
+                else {
+                    esResponseCode = -3;
+                }
             } catch (Exception e) {
                 log.error("Indexing "+e.getMessage());
                 return -1;
diff --git a/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/reader/RunSPARQLQueryService.java b/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/reader/RunSPARQLQueryService.java
index 854c723..d9d0514 100644
--- a/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/reader/RunSPARQLQueryService.java
+++ b/dnet-ariadneplus-graphdb-publisher/src/main/java/eu/dnetlib/ariadneplus/reader/RunSPARQLQueryService.java
@@ -63,6 +63,7 @@ public class RunSPARQLQueryService {
 		if (queryTemplate==null)
 			return null;
 		final String selectQueryTemplate = queryTemplate.replaceAll("%datasource", datasource).replaceAll("%collectionId", collectionId);
+		log.info("Start indexing "+ recordIds.size()+ " records ...");
 		recordIds.forEach(recordId -> {
 			int operationResult = executeQueryGraph(selectQueryTemplate, recordId, isCollection);
 			log.info("Indexing final code: "+Integer.toString(operationResult));
@@ -71,9 +72,9 @@ public class RunSPARQLQueryService {
 	}
 
     private int executeQueryGraph(String selectQueryTemplate, String recordId, boolean isCollection){
-		// to avoid heap overload on graphdb
+		// decrease queries execution rate to avoid heap overload on graphdb
 		try {
-			Thread.sleep(100);
+			Thread.sleep(50);
 		} catch (InterruptedException e) {
 			e.printStackTrace();
 		}