diff --git a/arangod/VocBase/compactor.cpp b/arangod/VocBase/compactor.cpp
index 649bf328f0..553d7bac22 100644
--- a/arangod/VocBase/compactor.cpp
+++ b/arangod/VocBase/compactor.cpp
@@ -1452,6 +1452,9 @@ void TRI_CompactorVocBase(void* data) {
             continue;
           }
 
+          // read-unlock the compaction lock later
+          TRI_DEFER(TRI_WriteUnlockReadWriteLock(&document->_compactionLock));
+
           try {
             if (document->_lastCompaction + COMPACTOR_COLLECTION_INTERVAL <=
                 now) {
@@ -1485,9 +1488,6 @@ void TRI_CompactorVocBase(void* data) {
             // in case an error occurs, we must still relase the lock
             LOG_ERROR("an unknown exception occurred during compaction");
           }
-
-          // read-unlock the compaction lock
-          TRI_WriteUnlockReadWriteLock(&document->_compactionLock);
         }
 
         TRI_READ_UNLOCK_STATUS_VOCBASE_COL(collection);
diff --git a/arangod/Wal/CollectorThread.cpp b/arangod/Wal/CollectorThread.cpp
index 100812a394..29c9877eaf 100644
--- a/arangod/Wal/CollectorThread.cpp
+++ b/arangod/Wal/CollectorThread.cpp
@@ -697,6 +697,124 @@ size_t CollectorThread::numQueuedOperations() {
   return _operationsQueue.size();
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief process a single marker in collector step 2
+////////////////////////////////////////////////////////////////////////////////
+
+void CollectorThread::processCollectionMarker(arangodb::arango::SingleCollectionWriteTransaction<UINT64_MAX>& trx,
+                                              TRI_document_collection_t* document,
+                                              CollectorCache* cache,
+                                              CollectorOperation const& operation) {
+  TRI_df_marker_t const* walMarker =
+      reinterpret_cast<TRI_df_marker_t const*>(operation.walPosition);
+  TRI_df_marker_t const* marker =
+      reinterpret_cast<TRI_df_marker_t const*>(operation.datafilePosition);
+  TRI_voc_size_t const datafileMarkerSize = operation.datafileMarkerSize;
+  TRI_voc_fid_t const fid = operation.datafileId;
+
+  TRI_ASSERT(walMarker != nullptr);
+  TRI_ASSERT(marker != nullptr);
+
+  if (walMarker->_type == TRI_WAL_MARKER_DOCUMENT) {
+    auto& dfi = createDfi(cache, fid);
+    dfi.numberUncollected--;
+
+    wal::document_marker_t const* m =
+        reinterpret_cast<wal::document_marker_t const*>(walMarker);
+    char const* key = reinterpret_cast<char const*>(m) + m->_offsetKey;
+
+    auto found = document->primaryIndex()->lookupKey(&trx, key);
+
+    if (found == nullptr || found->_rid != m->_revisionId ||
+        found->getDataPtr() != walMarker) {
+      // somebody inserted a new revision of the document or the revision
+      // was already moved by the compactor
+      dfi.numberDead++;
+      dfi.sizeDead += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+    } else {
+      // update cap constraint info
+      document->_headersPtr->adjustTotalSize(
+          TRI_DF_ALIGN_BLOCK(walMarker->_size),
+          TRI_DF_ALIGN_BLOCK(datafileMarkerSize));
+
+      // we can safely update the master pointer's dataptr value
+      found->setDataPtr(static_cast<void*>(
+          const_cast<char*>(operation.datafilePosition)));
+      found->_fid = fid;
+      
+      dfi.numberAlive++;
+      dfi.sizeAlive += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+    }
+  } else if (walMarker->_type == TRI_WAL_MARKER_EDGE) {
+    auto& dfi = createDfi(cache, fid);
+    dfi.numberUncollected--;
+
+    wal::edge_marker_t const* m =
+        reinterpret_cast<wal::edge_marker_t const*>(walMarker);
+    char const* key = reinterpret_cast<char const*>(m) + m->_offsetKey;
+
+    auto found = document->primaryIndex()->lookupKey(&trx, key);
+
+    if (found == nullptr || found->_rid != m->_revisionId ||
+        found->getDataPtr() != walMarker) {
+      // somebody inserted a new revision of the document or the revision
+      // was already moved by the compactor
+      dfi.numberDead++;
+      dfi.sizeDead += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+    } else {
+      // update cap constraint info
+      document->_headersPtr->adjustTotalSize(
+          TRI_DF_ALIGN_BLOCK(walMarker->_size),
+          TRI_DF_ALIGN_BLOCK(datafileMarkerSize));
+
+      // we can safely update the master pointer's dataptr value
+      found->setDataPtr(static_cast<void*>(
+          const_cast<char*>(operation.datafilePosition)));
+      found->_fid = fid;
+      
+      dfi.numberAlive++;
+      dfi.sizeAlive += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+    }
+  } else if (walMarker->_type == TRI_WAL_MARKER_REMOVE) {
+    auto& dfi = createDfi(cache, fid);
+    dfi.numberUncollected--;
+    dfi.numberDeletions++;
+
+    wal::remove_marker_t const* m =
+        reinterpret_cast<wal::remove_marker_t const*>(walMarker);
+    char const* key =
+        reinterpret_cast<char const*>(m) + sizeof(wal::remove_marker_t);
+
+    auto found = document->primaryIndex()->lookupKey(&trx, key);
+
+    if (found != nullptr && found->_rid > m->_revisionId) {
+      // somebody re-created the document with a newer revision
+      dfi.numberDead++;
+      dfi.sizeDead += (int64_t) TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+    }
+  } else if (walMarker->_type == TRI_WAL_MARKER_ATTRIBUTE) {
+    // move the pointer to the attribute from WAL to the datafile
+    document->getShaper()->moveMarker(
+        const_cast<TRI_df_marker_t*>(marker),
+        (void*)walMarker);  // ONLY IN COLLECTOR, PROTECTED by COLLECTION
+                            // LOCK and fake trx here
+    auto& dfi = createDfi(cache, fid);
+    dfi.numberUncollected--;
+    dfi.numberAttributes++;
+    dfi.sizeAttributes += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+  } else if (walMarker->_type == TRI_WAL_MARKER_SHAPE) {
+    // move the pointer to the shape from WAL to the datafile
+    document->getShaper()->moveMarker(
+        const_cast<TRI_df_marker_t*>(marker),
+        (void*)walMarker);  // ONLY IN COLLECTOR, PROTECTED by COLLECTION
+                            // LOCK and fake trx here
+    auto& dfi = createDfi(cache, fid);
+    dfi.numberUncollected--;
+    dfi.numberShapes++;
+    dfi.sizeShapes += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
+  }
+}      
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief process all operations for a single collection
 ////////////////////////////////////////////////////////////////////////////////
@@ -750,120 +868,8 @@ int CollectorThread::processCollectionOperations(CollectorCache* cache) {
 
     TRI_ASSERT(!cache->operations->empty());
 
-    auto primaryIndex = document->primaryIndex();
-
-    for (auto it = cache->operations->begin(); it != cache->operations->end();
-         ++it) {
-      auto operation = (*it);
-
-      TRI_df_marker_t const* walMarker =
-          reinterpret_cast<TRI_df_marker_t const*>(operation.walPosition);
-      TRI_df_marker_t const* marker =
-          reinterpret_cast<TRI_df_marker_t const*>(operation.datafilePosition);
-      TRI_voc_size_t const datafileMarkerSize = operation.datafileMarkerSize;
-      TRI_voc_fid_t const fid = operation.datafileId;
-
-      TRI_ASSERT(walMarker != nullptr);
-      TRI_ASSERT(marker != nullptr);
-
-      if (walMarker->_type == TRI_WAL_MARKER_DOCUMENT) {
-        auto& dfi = createDfi(cache, fid);
-        dfi.numberUncollected--;
-
-        wal::document_marker_t const* m =
-            reinterpret_cast<wal::document_marker_t const*>(walMarker);
-        char const* key = reinterpret_cast<char const*>(m) + m->_offsetKey;
-
-        auto found = primaryIndex->lookupKey(&trx, key);
-
-        if (found == nullptr || found->_rid != m->_revisionId ||
-            found->getDataPtr() != walMarker) {
-          // somebody inserted a new revision of the document or the revision
-          // was already moved by the compactor
-          dfi.numberDead++;
-          dfi.sizeDead += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-        } else {
-          // update cap constraint info
-          document->_headersPtr->adjustTotalSize(
-              TRI_DF_ALIGN_BLOCK(walMarker->_size),
-              TRI_DF_ALIGN_BLOCK(datafileMarkerSize));
-
-          // we can safely update the master pointer's dataptr value
-          found->setDataPtr(static_cast<void*>(
-              const_cast<char*>(operation.datafilePosition)));
-          found->_fid = fid;
-          
-          dfi.numberAlive++;
-          dfi.sizeAlive += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-        }
-      } else if (walMarker->_type == TRI_WAL_MARKER_EDGE) {
-        auto& dfi = createDfi(cache, fid);
-        dfi.numberUncollected--;
-
-        wal::edge_marker_t const* m =
-            reinterpret_cast<wal::edge_marker_t const*>(walMarker);
-        char const* key = reinterpret_cast<char const*>(m) + m->_offsetKey;
-
-        auto found = primaryIndex->lookupKey(&trx, key);
-
-        if (found == nullptr || found->_rid != m->_revisionId ||
-            found->getDataPtr() != walMarker) {
-          // somebody inserted a new revision of the document or the revision
-          // was already moved by the compactor
-          dfi.numberDead++;
-          dfi.sizeDead += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-        } else {
-          // update cap constraint info
-          document->_headersPtr->adjustTotalSize(
-              TRI_DF_ALIGN_BLOCK(walMarker->_size),
-              TRI_DF_ALIGN_BLOCK(datafileMarkerSize));
-
-          // we can safely update the master pointer's dataptr value
-          found->setDataPtr(static_cast<void*>(
-              const_cast<char*>(operation.datafilePosition)));
-          found->_fid = fid;
-          
-          dfi.numberAlive++;
-          dfi.sizeAlive += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-        }
-      } else if (walMarker->_type == TRI_WAL_MARKER_REMOVE) {
-        auto& dfi = createDfi(cache, fid);
-        dfi.numberUncollected--;
-        dfi.numberDeletions++;
-
-        wal::remove_marker_t const* m =
-            reinterpret_cast<wal::remove_marker_t const*>(walMarker);
-        char const* key =
-            reinterpret_cast<char const*>(m) + sizeof(wal::remove_marker_t);
-
-        auto found = primaryIndex->lookupKey(&trx, key);
-
-        if (found != nullptr && found->_rid > m->_revisionId) {
-          // somebody re-created the document with a newer revision
-          dfi.numberDead++;
-          dfi.sizeDead += (int64_t) TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-        }
-      } else if (walMarker->_type == TRI_WAL_MARKER_ATTRIBUTE) {
-        // move the pointer to the attribute from WAL to the datafile
-        document->getShaper()->moveMarker(
-            const_cast<TRI_df_marker_t*>(marker),
-            (void*)walMarker);  // ONLY IN COLLECTOR, PROTECTED by COLLECTION
-                                // LOCK and fake trx here
-        auto& dfi = createDfi(cache, fid);
-        dfi.numberUncollected--;
-        dfi.numberAttributes++;
-        dfi.sizeAttributes += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-      } else if (walMarker->_type == TRI_WAL_MARKER_SHAPE) {
-        // move the pointer to the shape from WAL to the datafile
-        document->getShaper()->moveMarker(
-            const_cast<TRI_df_marker_t*>(marker),
-            (void*)walMarker);  // ONLY IN COLLECTOR, PROTECTED by COLLECTION
-                                // LOCK and fake trx here
-        auto& dfi = createDfi(cache, fid);
-        dfi.numberUncollected--;
-        dfi.numberShapes++;
-        dfi.sizeShapes += (int64_t)TRI_DF_ALIGN_BLOCK(datafileMarkerSize);
-      }
+    for (auto const& it : *(cache->operations)) {
+      processCollectionMarker(trx, document, cache, it);
     }
 
     // finally update all datafile statistics
diff --git a/arangod/Wal/CollectorThread.h b/arangod/Wal/CollectorThread.h
index 8120768265..065a63cce2 100644
--- a/arangod/Wal/CollectorThread.h
+++ b/arangod/Wal/CollectorThread.h
@@ -28,6 +28,7 @@
 #include "Basics/ConditionVariable.h"
 #include "Basics/Mutex.h"
 #include "Basics/Thread.h"
+#include "Utils/transactions.h"
 #include "VocBase/datafile.h"
 #include "VocBase/DatafileStatistics.h"
 #include "VocBase/Ditch.h"
@@ -252,6 +253,16 @@ class CollectorThread : public basics::Thread {
 
   
  private:
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief process a single marker in collector step 2
+  //////////////////////////////////////////////////////////////////////////////
+
+  void processCollectionMarker(arangodb::arango::SingleCollectionWriteTransaction<UINT64_MAX>&,
+                               TRI_document_collection_t*,
+                               CollectorCache*,
+                               CollectorOperation const&);
+
   //////////////////////////////////////////////////////////////////////////////
   /// @brief return the number of queued operations
   //////////////////////////////////////////////////////////////////////////////