diff --git a/modules/dcache/src/main/java/org/dcache/pool/classic/SimpleIoScheduler.java b/modules/dcache/src/main/java/org/dcache/pool/classic/SimpleIoScheduler.java
index 1c792288c6d..16d18abfc75 100644
--- a/modules/dcache/src/main/java/org/dcache/pool/classic/SimpleIoScheduler.java
+++ b/modules/dcache/src/main/java/org/dcache/pool/classic/SimpleIoScheduler.java
@@ -126,8 +126,17 @@ public synchronized int add(Mover<?> mover, IoPriority priority) {
             _log.warn("A task was added to queue '{}', however the queue is not configured to execute any tasks.", _name);
         }
 
-        PrioritizedRequest wrapper = new PrioritizedRequest(id, mover, priority);
-        _queue.add(wrapper);
+        final PrioritizedRequest wrapper = new PrioritizedRequest(id, mover, priority);
+
+        if (_semaphore.tryAcquire()) {
+            /*
+             * there is a free slot in the queue - use it!
+             */
+            sendToExecution(wrapper);
+        } else {
+            _queue.add(wrapper);
+        }
+
         _jobs.put(id, wrapper);
 
         return id;
@@ -284,58 +293,10 @@ public void run() {
                 _semaphore.acquire();
                 try {
                     final PrioritizedRequest request = _queue.take();
-                    request.getCdc().restore();
-                    request.transfer(
-                            new CompletionHandler<Void,Void>()
-                            {
-                                @Override
-                                public void completed(Void result, Void attachment)
-                                {
-                                    postprocess();
-                                }
-
-                                @Override
-                                public void failed(Throwable exc, Void attachment)
-                                {
-                                    if (exc instanceof InterruptedException || exc instanceof InterruptedIOException) {
-                                        request.getMover().setTransferStatus(CacheException.DEFAULT_ERROR_CODE, "Transfer was killed");
-                                    }
-                                    postprocess();
-                                }
-
-                                private void postprocess()
-                                {
-                                    request.getMover().postprocess(
-                                            new CompletionHandler<Void, Void>()
-                                            {
-                                                @Override
-                                                public void completed(Void result,
-                                                                      Void attachment)
-                                                {
-                                                    release();
-                                                }
-
-                                                @Override
-                                                public void failed(Throwable exc,
-                                                                   Void attachment)
-                                                {
-                                                    release();
-                                                }
-
-                                                private void release()
-                                                {
-                                                    request.done();
-                                                    _jobs.remove(request.getId());
-                                                    _semaphore.release();
-                                                }
-                                            });
-                                }
-                            });
+                    sendToExecution(request);
                 } catch (RuntimeException | Error | InterruptedException e) {
                     _semaphore.release();
                     throw e;
-                } finally {
-                    CDC.clear();
                 }
             }
         } catch (InterruptedException e) {
@@ -343,6 +304,47 @@ private void release()
         }
     }
 
+    private void sendToExecution(final PrioritizedRequest request) {
+        try (CDC ignore = request.getCdc().restore()) {
+            request.transfer(
+                    new CompletionHandler<Void, Void>() {
+                        @Override
+                        public void completed(Void result, Void attachment) {
+                            postprocess();
+                        }
+
+                        @Override
+                        public void failed(Throwable exc, Void attachment) {
+                            if (exc instanceof InterruptedException || exc instanceof InterruptedIOException) {
+                                request.getMover().setTransferStatus(CacheException.DEFAULT_ERROR_CODE, "Transfer was killed");
+                            }
+                            postprocess();
+                        }
+
+                        private void postprocess() {
+                            request.getMover().postprocess(
+                                    new CompletionHandler<Void, Void>() {
+                                        @Override
+                                        public void completed(Void result, Void attachment) {
+                                            release();
+                                        }
+
+                                        @Override
+                                        public void failed(Throwable exc, Void attachment) {
+                                            release();
+                                        }
+
+                                        private void release() {
+                                            request.done();
+                                            _jobs.remove(request.getId());
+                                            _semaphore.release();
+                                        }
+                                    });
+                        }
+                    });
+        }
+    }
+
     private static class PrioritizedRequest implements IoPrioritizable  {
         private final Mover<?> _mover;
         private final IoPriority _priority;