diff --git a/arangod/VocBase/replication.c b/arangod/VocBase/replication.c
index 72f2e0f05e..b35fbc4199 100644
--- a/arangod/VocBase/replication.c
+++ b/arangod/VocBase/replication.c
@@ -56,18 +56,6 @@
 /// @{
 ////////////////////////////////////////////////////////////////////////////////
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief number of pre-allocated string buffers for logging
-////////////////////////////////////////////////////////////////////////////////
-
-#define NUM_BUFFERS 8
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief pre-allocated size for each log buffer
-////////////////////////////////////////////////////////////////////////////////
-
-#define BUFFER_SIZE 256
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief shortcut function
 ////////////////////////////////////////////////////////////////////////////////
@@ -111,6 +99,31 @@
 /// @}
 ////////////////////////////////////////////////////////////////////////////////
 
+// -----------------------------------------------------------------------------
+// --SECTION--                                                 private variables
+// -----------------------------------------------------------------------------
+
+////////////////////////////////////////////////////////////////////////////////
+/// @addtogroup VocBase
+/// @{
+////////////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief number of pre-allocated string buffers for logging
+////////////////////////////////////////////////////////////////////////////////
+
+static size_t NumBuffers = 8;
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief pre-allocated size for each log buffer
+////////////////////////////////////////////////////////////////////////////////
+
+static size_t BufferSize = 256;
+
+////////////////////////////////////////////////////////////////////////////////
+/// @}
+////////////////////////////////////////////////////////////////////////////////
+
 // -----------------------------------------------------------------------------
 // --SECTION--                                                     private types
 // -----------------------------------------------------------------------------
@@ -119,6 +132,10 @@
 /// @addtogroup VocBase
 /// @{
 ////////////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief a datafile descriptor
+////////////////////////////////////////////////////////////////////////////////
   
 typedef struct {
   TRI_datafile_t* _data;
@@ -279,7 +296,7 @@ static void ReturnBuffer (TRI_replication_logger_t* logger,
 
   // make the buffer usable again
   if (buffer->_buffer == NULL) {
-    TRI_InitSizedStringBuffer(buffer, TRI_CORE_MEM_ZONE, BUFFER_SIZE);
+    TRI_InitSizedStringBuffer(buffer, TRI_CORE_MEM_ZONE, BufferSize);
   }
   else {
     TRI_ResetStringBuffer(buffer);
@@ -290,7 +307,7 @@ static void ReturnBuffer (TRI_replication_logger_t* logger,
   TRI_LockSpin(&logger->_bufferLock);
 
   TRI_PushBackVectorPointer(&logger->_buffers, buffer);
-  assert(logger->_buffers._length <= NUM_BUFFERS);
+  assert(logger->_buffers._length <= NumBuffers);
   
   TRI_UnlockSpin(&logger->_bufferLock);
   // ---------------------------------------
@@ -304,7 +321,7 @@ static void ReturnBuffer (TRI_replication_logger_t* logger,
 
 static int LogEvent (TRI_replication_logger_t* logger,
                      TRI_voc_tid_t tid,
-                     bool lock,
+                     bool isStandaloneOperation,
                      TRI_replication_operation_e type,
                      TRI_string_buffer_t* buffer) {
   TRI_primary_collection_t* primary;
@@ -313,6 +330,7 @@ static int LogEvent (TRI_replication_logger_t* logger,
   TRI_doc_mptr_t mptr;
   size_t len;
   int res;
+  bool forceSync;
   bool withTid;
 
   assert(logger != NULL);
@@ -327,7 +345,11 @@ static int LogEvent (TRI_replication_logger_t* logger,
     return TRI_ERROR_NO_ERROR;
   }
 
+  // do we have a transaction id?
   withTid = (tid > 0);
+
+  // this type of operation will be synced. all other operations will not be synced.
+  forceSync = (type == REPLICATION_STOP);
  
   // TODO: instead of using JSON here, we could directly use ShapedJson.
   // this will be a performance optimisation
@@ -390,8 +412,8 @@ static int LogEvent (TRI_replication_logger_t* logger,
                         TRI_DOC_MARKER_KEY_DOCUMENT, 
                         shaped, 
                         NULL, 
-                        lock, 
-                        false);
+                        isStandaloneOperation, 
+                        forceSync);
 
   TRI_FreeShapedJson(primary->_shaper, shaped);
 
@@ -1472,7 +1494,7 @@ static int StopReplicationLogger (TRI_replication_logger_t* logger) {
   }
 
   res = LogEvent(logger, 0, true, REPLICATION_STOP, buffer); 
-  
+
   TRI_CommitTransaction(logger->_trx, 0);
   TRI_FreeTransaction(logger->_trx);
   
@@ -1548,18 +1570,18 @@ static int InitBuffers (TRI_replication_logger_t* logger) {
   size_t i;
   int res;
 
-  assert(NUM_BUFFERS > 0);
+  assert(NumBuffers > 0);
   
   LOG_TRACE("initialising buffers");
 
-  res = TRI_InitVectorPointer2(&logger->_buffers, TRI_CORE_MEM_ZONE, NUM_BUFFERS);
+  res = TRI_InitVectorPointer2(&logger->_buffers, TRI_CORE_MEM_ZONE, NumBuffers); 
 
   if (res != TRI_ERROR_NO_ERROR) {
     return res;
   }
 
-  for (i = 0; i < NUM_BUFFERS; ++i) {
-    TRI_string_buffer_t* buffer = TRI_CreateSizedStringBuffer(TRI_CORE_MEM_ZONE, BUFFER_SIZE);
+  for (i = 0; i < NumBuffers; ++i) {
+    TRI_string_buffer_t* buffer = TRI_CreateSizedStringBuffer(TRI_CORE_MEM_ZONE, BufferSize);
 
     if (buffer == NULL) {
       FreeBuffers(logger);
@@ -1570,7 +1592,7 @@ static int InitBuffers (TRI_replication_logger_t* logger) {
     TRI_PushBackVectorPointer(&logger->_buffers, buffer);
   }
 
-  assert(logger->_buffers._length == NUM_BUFFERS);
+  assert(logger->_buffers._length == NumBuffers);
 
   return TRI_ERROR_NO_ERROR;
 }
@@ -1853,6 +1875,8 @@ int TRI_LogTransactionReplication (TRI_vocbase_t* vocbase,
 
     primary = logger->_trxCollection->_collection->_collection;
 
+    assert(primary != NULL);
+
     // set a lock around all individual operations
     // so a transaction is logged as an uninterrupted sequence
     primary->beginWrite(primary);