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 b29be6e..96222b4 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
@@ -7,6 +7,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.eclipse.rdf4j.model.Model;
 import org.eclipse.rdf4j.query.*;
+import org.eclipse.rdf4j.repository.http.HTTPQueryEvaluationException;
 import org.eclipse.rdf4j.repository.Repository;
 import org.eclipse.rdf4j.repository.RepositoryConnection;
 import org.eclipse.rdf4j.repository.manager.RemoteRepositoryManager;
@@ -70,17 +71,35 @@ public class RunSPARQLQueryService {
 		final List<Integer> successCodesCount = Arrays.asList(new Integer(0));
 		final List<Integer> counter = Arrays.asList(new Integer(0));
 		recordIds.forEach(recordId -> {
-			log.debug(recordId+" >");
+			int waitAmount=1;
 			int operationResult = executeQueryGraph(selectQueryTemplate, recordId, isCollection);
-			log.debug(" "+operationResult);
 			if (operationResult!=200) {
 				log.error(recordId + " error_code: "+ operationResult);
-				if (isCollection) {
-					throw new RuntimeException("Collection indexing problem - errcode: "+operationResult);
+				if (operationResult==-5) {
+					do {
+						// let's wait if heap space decreases
+						try {
+							log.warn("Waiting more free space on heap for " + waitAmount + " seconds ...");
+							Thread.sleep(waitAmount * 1000);
+							waitAmount = waitAmount*2;
+						} catch (InterruptedException ie) {
+							log.error(ie);
+						}
+						int retryResult = 0;
+						retryResult = executeQueryGraph(selectQueryTemplate, recordId, isCollection);
+						log.debug("retryResult: " + retryResult);
+					} while (retryResult!=200);
+				}
+				if (operationResult!=200) {
+					int currentErrorsCount = errorCodesCount.get(0).intValue();
+					currentErrorsCount += 1;
+					errorCodesCount.set(0, new Integer(currentErrorsCount));
+				}
+				else {
+					int currentSuccessCount = successCodesCount.get(0).intValue();
+					currentSuccessCount+=1;
+					successCodesCount.set(0, new Integer(currentSuccessCount));
 				}
-				int currentErrorsCount = errorCodesCount.get(0).intValue();
-				currentErrorsCount+=1;
-				errorCodesCount.set(0, new Integer(currentErrorsCount));
 			}
 			else {
 				int currentSuccessCount = successCodesCount.get(0).intValue();
@@ -140,7 +159,10 @@ public class RunSPARQLQueryService {
 			}
 			resourceManager.manage(parser);
 			return bulkUpload.index(resourceManager, isCollection);
-        } catch(Exception e){
+        } catch (HTTPQueryEvaluationException qe) {
+			log.error(qe);
+			return -5;
+		} catch(Exception e){
             log.error(e);
             return -1;
         } finally{