diff --git a/src/octopus/dispatcher/db/pulidb.py b/src/octopus/dispatcher/db/pulidb.py
index 3ee9df7e..475215a2 100644
--- a/src/octopus/dispatcher/db/pulidb.py
+++ b/src/octopus/dispatcher/db/pulidb.py
@@ -256,7 +256,7 @@ def createElements(self, elements):
                 conn = TaskNodes._connection
                 fields = {TaskNodes.q.id.fieldName: element.id,
                           TaskNodes.q.name.fieldName: element.name,
-                          TaskNodes.q.parentId.fieldName: element.parent.id if element.parent else None,
+                          TaskNodes.q.parentId.fieldName: element.parent.id,
                           TaskNodes.q.user.fieldName: element.user,
                           TaskNodes.q.priority.fieldName: element.priority,
                           TaskNodes.q.dispatchKey.fieldName: element.dispatchKey,
diff --git a/src/octopus/dispatcher/dispatcher.py b/src/octopus/dispatcher/dispatcher.py
index a4cd1f65..d386a2f7 100644
--- a/src/octopus/dispatcher/dispatcher.py
+++ b/src/octopus/dispatcher/dispatcher.py
@@ -459,13 +459,19 @@ def computeAssignments(self):
             # If we have dedicated render nodes for this poolShare
             if not any([poolShare.hasRenderNodesAvailable() for poolShare in entryPoint.poolShares.values()]):
                 continue
-
-            for (rn, com) in entryPoint.dispatchIterator(lambda: self.queue.qsize() > 0):
-                assignments.append((rn, com))
-                # increment the allocatedRN for the poolshare
-                entryPoint.mainPoolShare().allocatedRN += 1
-                # save the active poolshare of the rendernode
-                rn.currentpoolshare = entryPoint.mainPoolShare()
+	    
+	    try:
+	        for (rn, com) in entryPoint.dispatchIterator(lambda: self.queue.qsize() > 0):
+        	    assignments.append((rn, com))
+        	    # increment the allocatedRN for the poolshare
+        	    entryPoint.mainPoolShare().allocatedRN += 1
+        	    # save the active poolshare of the rendernode
+        	    rn.currentpoolshare = entryPoint.mainPoolShare()
+	    except NoRenderNodeAvailable:
+                 pass
+ 	    except NoLicenseAvailableForTask:
+                 LOGGER.info("Missing license for node \"%s\" (other commands can start anyway)." % entryPoint.name)
+		 pass
 
         assignmentDict = collections.defaultdict(list)
         for (rn, com) in assignments:
diff --git a/src/octopus/dispatcher/model/node.py b/src/octopus/dispatcher/model/node.py
index ecb4404b..593e7599 100644
--- a/src/octopus/dispatcher/model/node.py
+++ b/src/octopus/dispatcher/model/node.py
@@ -557,24 +557,21 @@ def reserve_rendernode(self, command, ep):
         if ep is None:
             ep = self
 
-        # PRA : can we have several poolShares for one job ?
-        # Exception when the pool of a job is changed and some command are still in computation
-        for poolShare in ep.poolShares.values():
-            # We need some RNs dedicated to this job available
-            if not poolShare.hasRenderNodesAvailable():
-                raise NoRenderNodeAvailable
-
-            # Sort the RNs according to their performance value
-            rnList = sorted(poolShare.pool.renderNodes, key=lambda rn: rn.performance, reverse=True)
+        for poolshare in [poolShare for poolShare in ep.poolShares.values() if poolShare.hasRenderNodesAvailable()]:
+            # first, sort the rendernodes according their performance value
+            rnList = sorted(poolshare.pool.renderNodes, key=lambda rn: rn.performance, reverse=True)
             for rendernode in rnList:
-                # Check for a suitable RN : ie available and respecting the constraints for this command
                 if rendernode.isAvailable() and rendernode.canRun(command):
-                    # Check licence
-                    if not rendernode.reserveLicense(command, self.dispatcher.licenseManager):
+                    if rendernode.reserveLicense(command, self.dispatcher.licenseManager):
+                        rendernode.addAssignment(command)
+                        return rendernode
+                    else:
                         raise NoLicenseAvailableForTask
-                    rendernode.addAssignment(command)
-                    return rendernode
-        # PRA : Can happen if there are available RNs but they don't match the command constraint
+
+        # Might not be necessary anymore because first loop is based on poolShare's hasRNSavailable method
+        # It was not taking into account the tests before assignment: RN.canRun()
+        if not [poolShare for poolShare in ep.poolShares.values() if poolShare.hasRenderNodesAvailable()]:
+            raise NoRenderNodeAvailable
         return None
 
     def updateCompletionAndStatus(self):