diff --git a/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp b/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
index 2d99be825ec..0e9479eb121 100644
--- a/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
+++ b/thorlcr/activities/lookupjoin/thlookupjoinslave.cpp
@@ -950,7 +950,7 @@ class CInMemJoinBase : public CSlaveActivity, public CAllOrLookupHelper<HELPER>,
         }
     } *rowProcessor;
 
-    CriticalSection rhsRowLock;
+    mutable CriticalSection rhsRowLock;
     Owned<CBroadcaster> broadcaster;
     CBroadcaster *channel0Broadcaster;
     CriticalSection *broadcastLock;
@@ -1812,6 +1812,7 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
     Owned<CFileOwner> overflowWriteFile;
     Owned<IExtRowWriter> overflowWriteStream;
     OwnedIFileIO overflowWriteFileIO;
+    mutable CriticalSection critOverflowWriteFileIO;
     rowcount_t overflowWriteCount;
     OwnedMalloc<IChannelDistributor *> channelDistributors;
     unsigned nextRhsToSpill = 0;
@@ -2101,11 +2102,14 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
             {
                 overflowWriteCount = 0;
                 overflowWriteStream.clear();
-                if (overflowWriteFileIO)
                 {
-                    mergeRemappedStats(PARENT::inactiveStats, overflowWriteFileIO, diskToTempStatsMap);
-                    overflowWriteFile->noteSize(overflowWriteFileIO->getStatistic(StSizeDiskWrite));
-                    overflowWriteFileIO.clear();
+                    CriticalBlock b(critOverflowWriteFileIO);
+                    if (overflowWriteFileIO)
+                    {
+                        mergeRemappedStats(PARENT::inactiveStats, overflowWriteFileIO, diskToTempStatsMap);
+                        overflowWriteFile->noteSize(overflowWriteFileIO->getStatistic(StSizeDiskWrite));
+                        overflowWriteFileIO.clear();
+                    }
                 }
                 overflowWriteFile.clear();
                 rightRowManager->addRowBuffer(this);
@@ -2165,8 +2169,8 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
                     ForEachItemIn(a, rhsSlaveRows)
                     {
                         CThorSpillableRowArray &rows = *rhsSlaveRows.item(a);
-                        rhs.appendRows(rows, true); // NB: This should not cause spilling, rhs is already sized and we are only copying ptrs in
                         mergeStats(PARENT::inactiveStats, &rows);
+                        rhs.appendRows(rows, true); // NB: This should not cause spilling, rhs is already sized and we are only copying ptrs in
                         rows.kill(); // free up ptr table asap
                     }
                     // Have to keep broadcastSpillingLock locked until sort and calculate are done
@@ -2562,6 +2566,7 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
          */
 
         Owned<IThorRowCollector> rightCollector;
+        Owned<IException> exception;
         try
         {
             CMarker marker(*this);
@@ -2686,16 +2691,19 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
         catch (IException *e)
         {
             if (!isOOMException(e))
-                throw e;
-            IOutputMetaData *inputOutputMeta = rightITDL->queryFromActivity()->queryContainer().queryHelper()->queryOutputMeta();
-            // rows may either be in separate slave row arrays or in single rhs array, or split.
-            rowcount_t total = rightCollector ? rightCollector->numRows() : (getGlobalRHSTotal() + rhs.ordinality());
-            if (rightCollector && rightCollector->hasSpilt())
-                mergeStats(PARENT::inactiveStats, rightCollector);
-            throw checkAndCreateOOMContextException(this, e, "gathering RHS rows for lookup join", total, inputOutputMeta, NULL);
+                exception.setown(e);
+            else
+            {
+                IOutputMetaData *inputOutputMeta = rightITDL->queryFromActivity()->queryContainer().queryHelper()->queryOutputMeta();
+                // rows may either be in separate slave row arrays or in single rhs array, or split.
+                rowcount_t total = rightCollector ? rightCollector->numRows() : (getGlobalRHSTotal() + rhs.ordinality());
+                exception.setown(checkAndCreateOOMContextException(this, e, "gathering RHS rows for lookup join", total, inputOutputMeta, NULL));
+            }
         }
         if (rightCollector && rightCollector->hasSpilt())
             mergeStats(PARENT::inactiveStats, rightCollector);
+        if (exception)
+            throw exception.getClear();
     }
 public:
     static bool needDedup(IHThorHashJoinArg *helper)
@@ -3035,12 +3043,18 @@ class CLookupJoinActivityBase : public CInMemJoinBase<HTHELPER, IHThorHashJoinAr
                 activeStats.setStatistic(StNumSmartJoinDegradedToLocal, aggregateFailoversToLocal); // NB: is going to be same for all slaves.
             activeStats.setStatistic(StNumSmartJoinSlavesDegradedToStd, aggregateFailoversToStandard);
         }
-        if (overflowWriteFileIO)
-            mergeRemappedStats(activeStats, overflowWriteFileIO, diskToTempStatsMap);
-        ForEachItemIn(a, rhsSlaveRows)
         {
-           CThorSpillableRowArray &rows = *rhsSlaveRows.item(a);
-           mergeStats(activeStats, &rows);
+            CriticalBlock b(critOverflowWriteFileIO);
+            if (overflowWriteFileIO)
+                mergeRemappedStats(activeStats, overflowWriteFileIO, diskToTempStatsMap);
+        }
+        {
+            CriticalBlock b(rhsRowLock);
+            ForEachItemIn(a, rhsSlaveRows)
+            {
+                CThorSpillableRowArray &rows = *rhsSlaveRows.item(a);
+                mergeRemappedStats(activeStats, &rows, diskToTempStatsMap);
+            }
         }
     }
 };
diff --git a/thorlcr/thorutil/thmem.cpp b/thorlcr/thorutil/thmem.cpp
index 9845fc6e35a..8eb1cb6f5cd 100644
--- a/thorlcr/thorutil/thmem.cpp
+++ b/thorlcr/thorutil/thmem.cpp
@@ -1333,13 +1333,13 @@ void CThorSpillableRowArray::safeUnregisterWriteCallback(IWritePosCallback &cb)
 }
 
 CThorSpillableRowArray::CThorSpillableRowArray(CActivityBase &activity)
-    : CThorExpandingRowArray(activity), inactiveStats(spillStatistics)
+    : CThorExpandingRowArray(activity), stats(tempFileStatistics)
 {
     throwOnOom = false;
 }
 
 CThorSpillableRowArray::CThorSpillableRowArray(CActivityBase &activity, IThorRowInterfaces *rowIf, EmptyRowSemantics emptyRowSemantics, StableSortFlag stableSort, rowidx_t initialSize, size32_t _commitDelta)
-    : CThorExpandingRowArray(activity, rowIf, ers_forbidden, stableSort, false, initialSize), commitDelta(_commitDelta), inactiveStats(spillStatistics)
+    : CThorExpandingRowArray(activity, rowIf, ers_forbidden, stableSort, false, initialSize), commitDelta(_commitDelta), stats(tempFileStatistics)
 {
 }
 
@@ -1368,7 +1368,7 @@ void CThorSpillableRowArray::kill()
 {
     clearRows();
     CThorExpandingRowArray::kill();
-    inactiveStats.reset();
+    stats.reset();
 }
 
 void CThorSpillableRowArray::sort(ICompare &compare, unsigned maxCores)
@@ -1469,10 +1469,10 @@ rowidx_t CThorSpillableRowArray::save(CFileOwner &iFileOwner, unsigned _spillCom
     firstRow += n;
     offset_t bytesWritten = writer->getPosition();
     writer.clear();
-    mergeRemappedStats(inactiveStats, iFileIO, diskToTempStatsMap);
+    mergeStats(stats, iFileIO);
     offset_t sizeTempFile = iFileIO->getStatistic(StSizeDiskWrite);
     iFileOwner.noteSize(sizeTempFile);
-    inactiveStats.addStatistic(StNumSpills, 1);
+    stats.addStatistic(StNumSpills, 1);
     ActPrintLog(&activity, "%s: CThorSpillableRowArray::save done, rows written = %" RIPF "u, bytes = %" I64F "u, firstRow = %u", _tracingPrefix, rowsWritten, (__int64)bytesWritten, firstRow);
     return rowsWritten;
 }
diff --git a/thorlcr/thorutil/thmem.hpp b/thorlcr/thorutil/thmem.hpp
index bdcda28efbf..a89d4cdd0f2 100644
--- a/thorlcr/thorutil/thmem.hpp
+++ b/thorlcr/thorutil/thmem.hpp
@@ -413,7 +413,7 @@ class graph_decl CThorSpillableRowArray : private CThorExpandingRowArray, implem
     mutable CriticalSection cs;
     ICopyArrayOf<IWritePosCallback> writeCallbacks;
     size32_t compBlkSz = 0; // means use default
-    CRuntimeStatisticCollection inactiveStats; // reset after each kill
+    CRuntimeStatisticCollection stats; // reset after each kill
     bool _flush(bool force);
     void doFlush();
     inline bool needToMoveRows(bool force) { return (firstRow != 0 && (force || (firstRow >= commitRows/2))); }
@@ -486,7 +486,7 @@ class graph_decl CThorSpillableRowArray : private CThorExpandingRowArray, implem
     inline rowidx_t queryTotalRows() const { return CThorExpandingRowArray::ordinality(); } // includes uncommited rows
     inline unsigned __int64 getStatistic(StatisticKind kind) const
     {
-        return inactiveStats.getStatisticValue(kind);
+        return stats.getStatisticValue(kind);
     }
 
 // access to
diff --git a/thorlcr/thorutil/thormisc.cpp b/thorlcr/thorutil/thormisc.cpp
index a9e493e02e4..70bdedb9361 100644
--- a/thorlcr/thorutil/thormisc.cpp
+++ b/thorlcr/thorutil/thormisc.cpp
@@ -97,6 +97,7 @@ const StatisticsMapping hashDedupActivityStatistics({}, spillStatistics, diskWri
 const StatisticsMapping hashDistribActivityStatistics({StNumLocalRows, StNumRemoteRows, StSizeRemoteWrite}, basicActivityStatistics);
 const StatisticsMapping loopActivityStatistics({StNumIterations}, basicActivityStatistics);
 const StatisticsMapping graphStatistics({StNumExecutions, StSizeSpillFile, StSizeGraphSpill, StSizePeakTempDisk, StSizePeakEphemeralDisk, StTimeUser, StTimeSystem, StNumContextSwitches, StSizeMemory, StSizePeakMemory, StSizeRowMemory, StSizePeakRowMemory}, executeStatistics);
+const StatisticsMapping tempFileStatistics({StNumSpills}, diskRemoteStatistics);
 
 const StatKindMap diskToTempStatsMap
 ={ {StSizeDiskWrite, StSizeSpillFile},
diff --git a/thorlcr/thorutil/thormisc.hpp b/thorlcr/thorutil/thormisc.hpp
index 3159d58ad48..17ebe967e8b 100644
--- a/thorlcr/thorutil/thormisc.hpp
+++ b/thorlcr/thorutil/thormisc.hpp
@@ -167,6 +167,8 @@ extern graph_decl const StatisticsMapping soapcallActivityStatistics;
 extern graph_decl const StatisticsMapping indexReadFileStatistics;
 extern graph_decl const StatisticsMapping hashDedupActivityStatistics;
 extern graph_decl const StatisticsMapping hashDistribActivityStatistics;
+extern graph_decl const StatisticsMapping tempFileStatistics;
+
 
 // Maps disk related stats to spill stats
 extern graph_decl const std::map<StatisticKind, StatisticKind> diskToTempStatsMap;