diff --git a/datatypes/mcs_decimal.h b/datatypes/mcs_decimal.h
index b87db7ebf..94aa2a50b 100644
--- a/datatypes/mcs_decimal.h
+++ b/datatypes/mcs_decimal.h
@@ -82,7 +82,7 @@ constexpr uint8_t MAXLEGACYWIDTH = 8U;
 constexpr uint8_t MAXSCALEINC4AVG = 4U;
 constexpr int8_t IGNOREPRECISION = -1;
 
-const int64_t mcs_pow_10[19] =
+const uint64_t mcs_pow_10[20] =
 {
     1ULL,
     10ULL,
@@ -103,6 +103,7 @@ const int64_t mcs_pow_10[19] =
     10000000000000000ULL,
     100000000000000000ULL,
     1000000000000000000ULL,
+    10000000000000000000ULL,
 };
 const int128_t mcs_pow_10_128[20] =
 {
diff --git a/dbcon/execplan/windowfunctioncolumn.cpp b/dbcon/execplan/windowfunctioncolumn.cpp
index 21f09aa06..a6ba127fa 100644
--- a/dbcon/execplan/windowfunctioncolumn.cpp
+++ b/dbcon/execplan/windowfunctioncolumn.cpp
@@ -52,8 +52,6 @@ using namespace rowgroup;
 #include "joblisttypes.h"
 using namespace joblist;
 
-#include "widedecimalutils.h"
-
 #ifdef _MSC_VER
 #define strcasecmp stricmp
 #endif
@@ -389,7 +387,8 @@ void WindowFunctionColumn::adjustResultType()
 
     if (boost::iequals(fFunctionName, "SUM") ||
         boost::iequals(fFunctionName, "AVG") ||
-        boost::iequals(fFunctionName, "AVG_DISTINCT"))
+        boost::iequals(fFunctionName, "AVG_DISTINCT") ||
+        boost::iequals(fFunctionName, "PERCENTILE"))
     {
         if (fFunctionParms[0]->resultType().colDataType == CalpontSystemCatalog::DECIMAL ||
             fFunctionParms[0]->resultType().colDataType == CalpontSystemCatalog::UDECIMAL)
@@ -689,7 +688,7 @@ void WindowFunctionColumn::evaluate(Row& row, bool& isNull)
                 case 16:
                 {
                     int128_t dec = row.getInt128Field(fInputIndex);
-                    if (utils::isWideDecimalNullValue(dec))
+                    if (dec == datatypes::Decimal128Null)
                         isNull = true;
                     else
                     {
diff --git a/utils/regr/moda.cpp b/utils/regr/moda.cpp
index e1bc44a9a..7bc5b427d 100644
--- a/utils/regr/moda.cpp
+++ b/utils/regr/moda.cpp
@@ -21,6 +21,7 @@
 #include "moda.h"
 #include "bytestream.h"
 #include "objectreader.h"
+#include "columnwidth.h"
 
 using namespace mcsv1sdk;
 
@@ -186,7 +187,7 @@ mcsv1_UDAF::ReturnCode moda::init(mcsv1Context* context,
         {
             context->setColWidth(8);
         }
-        else
+        else if (utils::widthByPrecision(colTypes[0].precision))
         {
             context->setColWidth(16);
         }
diff --git a/utils/rowgroup/rowgroup.h b/utils/rowgroup/rowgroup.h
index 669220c21..748bf3dfa 100644
--- a/utils/rowgroup/rowgroup.h
+++ b/utils/rowgroup/rowgroup.h
@@ -962,11 +962,15 @@ inline long double Row::getLongDoubleField(uint32_t colIndex) const
     return *((long double*) &data[offsets[colIndex]]);
 }
 
+// !!! Never ever try to remove inline from this f() b/c it returns
+// non-integral 16 byte DT
 inline int128_t Row::getInt128Field(uint32_t colIndex) const
 {
     return *((int128_t*) &data[offsets[colIndex]]);
 }
 
+// !!! Never ever try to remove inline from this f() b/c it returns
+// non-integral 16 byte DT
 inline uint128_t Row::getUint128Field(uint32_t colIndex) const
 {
     return *((uint128_t*) &data[offsets[colIndex]]);
diff --git a/utils/windowfunction/idborderby.cpp b/utils/windowfunction/idborderby.cpp
index 6814ed4ad..1028d3e1d 100644
--- a/utils/windowfunction/idborderby.cpp
+++ b/utils/windowfunction/idborderby.cpp
@@ -856,11 +856,11 @@ bool EqualCompData::operator()(Row::Pointer a, Row::Pointer b)
             case CalpontSystemCatalog::UDECIMAL:
             {
                 // equal compare. ignore sign and null
-                if (fRow1.getColumnWidth(*i) < 16)
+                if (fRow1.getColumnWidth(*i) < datatypes::MAXDECIMALWIDTH)
                 {
                     eq = (fRow1.getUintField(*i) == fRow2.getUintField(*i));
                 }
-                else
+                else if (fRow1.getColumnWidth(*i) == datatypes::MAXDECIMALWIDTH)
                 {
                     eq = (fRow1.getUint128Field(*i) == fRow2.getUint128Field(*i));
                 }
diff --git a/utils/windowfunction/wf_count.cpp b/utils/windowfunction/wf_count.cpp
index d7e9b104e..29987c3b4 100644
--- a/utils/windowfunction/wf_count.cpp
+++ b/utils/windowfunction/wf_count.cpp
@@ -78,11 +78,11 @@ boost::shared_ptr<WindowFunctionType> WF_count<T>::makeFunction(int id, const st
         case CalpontSystemCatalog::DECIMAL:
         case CalpontSystemCatalog::UDECIMAL:
         {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
+            if (wc->functionParms()[0]->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_count<int64_t>(id, name));
             }
-            else
+            else if (wc->functionParms()[0]->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_count<int128_t>(id, name));
             }
diff --git a/utils/windowfunction/wf_lead_lag.cpp b/utils/windowfunction/wf_lead_lag.cpp
index f8aa32ca1..1a1b453cd 100644
--- a/utils/windowfunction/wf_lead_lag.cpp
+++ b/utils/windowfunction/wf_lead_lag.cpp
@@ -85,11 +85,11 @@ boost::shared_ptr<WindowFunctionType> WF_lead_lag<T>::makeFunction(int id, const
 
         case CalpontSystemCatalog::DECIMAL:
         {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
+            if (wc->functionParms()[0]->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_lead_lag<int64_t>(id, name));
             }
-            else
+            else if (wc->functionParms()[0]->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_lead_lag<int128_t>(id, name));
             }
diff --git a/utils/windowfunction/wf_nth_value.cpp b/utils/windowfunction/wf_nth_value.cpp
index 73b0bf1be..41dde88fb 100644
--- a/utils/windowfunction/wf_nth_value.cpp
+++ b/utils/windowfunction/wf_nth_value.cpp
@@ -84,31 +84,19 @@ boost::shared_ptr<WindowFunctionType> WF_nth_value<T>::makeFunction(int id, cons
         }
 
         case CalpontSystemCatalog::DECIMAL:
+        case CalpontSystemCatalog::UDECIMAL:
         {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
+            if (wc->functionParms()[0]->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_nth_value<int64_t>(id, name));
             }
-            else
+            else if (wc->functionParms()[0]->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_nth_value<int128_t>(id, name));
             }
             break;
         }
         
-        case CalpontSystemCatalog::UDECIMAL:
-        {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
-            {
-                func.reset(new WF_nth_value<uint64_t>(id, name));
-            }
-            else
-            {
-                func.reset(new WF_nth_value<uint128_t>(id, name));
-            }
-            break;
-        }
-
         case CalpontSystemCatalog::DOUBLE:
         case CalpontSystemCatalog::UDOUBLE:
         {
diff --git a/utils/windowfunction/wf_percentile.cpp b/utils/windowfunction/wf_percentile.cpp
index 8aaeba9f6..a407d41e8 100644
--- a/utils/windowfunction/wf_percentile.cpp
+++ b/utils/windowfunction/wf_percentile.cpp
@@ -46,6 +46,8 @@ using namespace ordering;
 #include "constantcolumn.h"
 using namespace execplan;
 
+#include "mcs_decimal.h"
+
 #include "windowfunctionstep.h"
 using namespace joblist;
 
@@ -89,31 +91,19 @@ boost::shared_ptr<WindowFunctionType> WF_percentile<T>::makeFunction(int id, con
             }
 
             case CalpontSystemCatalog::DECIMAL:
+            case CalpontSystemCatalog::UDECIMAL:
             {
-                if (wc->functionParms()[0]->resultType().colWidth < 16)
+                if (wc->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
                 {
                     func.reset(new WF_percentile<int64_t>(id, name));
                 }
-                else
+                else if (wc->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
                 {
                     func.reset(new WF_percentile<int128_t>(id, name));
                 }
                 break;
             }
             
-            case CalpontSystemCatalog::UDECIMAL:
-            {
-                if (wc->functionParms()[0]->resultType().colWidth < 16)
-                {
-                    func.reset(new WF_percentile<uint64_t>(id, name));
-                }
-                else
-                {
-                    func.reset(new WF_percentile<uint128_t>(id, name));
-                }
-                break;
-            }
-
             case CalpontSystemCatalog::DOUBLE:
             case CalpontSystemCatalog::UDOUBLE:
             {
diff --git a/utils/windowfunction/wf_stats.cpp b/utils/windowfunction/wf_stats.cpp
index 1804ad432..0dee4fa9e 100644
--- a/utils/windowfunction/wf_stats.cpp
+++ b/utils/windowfunction/wf_stats.cpp
@@ -82,30 +82,18 @@ boost::shared_ptr<WindowFunctionType> WF_stats<T>::makeFunction(int id, const st
         }
 
         case CalpontSystemCatalog::DECIMAL:
+        case CalpontSystemCatalog::UDECIMAL:
         {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
+            if (wc->functionParms()[0]->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_stats<int64_t>(id, name));
             }
-            else
+            else if (wc->functionParms()[0]->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_stats<int128_t>(id, name));
             }
             break;
         }
-        
-        case CalpontSystemCatalog::UDECIMAL:
-        {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
-            {
-                func.reset(new WF_stats<uint64_t>(id, name));
-            }
-            else
-            {
-                func.reset(new WF_stats<uint128_t>(id, name));
-            }
-            break;
-        }
 
         case CalpontSystemCatalog::DOUBLE:
         case CalpontSystemCatalog::UDOUBLE:
diff --git a/utils/windowfunction/wf_sum_avg.cpp b/utils/windowfunction/wf_sum_avg.cpp
index b61fb9928..007bb1fc7 100644
--- a/utils/windowfunction/wf_sum_avg.cpp
+++ b/utils/windowfunction/wf_sum_avg.cpp
@@ -52,35 +52,49 @@ using namespace joblist;
 
 namespace windowfunction
 {
-template<typename T_IN, typename T_OUT>
-void WF_sum_avg<T_IN, T_OUT>::checkSumLimit(long double val, long double sum)
-{
-}
 
 template<typename T_IN, typename T_OUT>
-inline void WF_sum_avg<T_IN, T_OUT>::checkSumLimit(int128_t val, int128_t sum)
+inline void WF_sum_avg<T_IN,T_OUT>::checkSumLimit(T_IN& val, T_OUT& sum)
+{ }
+
+template<>
+inline void WF_sum_avg<int128_t,int128_t>::checkSumLimit(int128_t& val, int128_t& sum)
 {
-    if (((sum >= 0) && ((fMax128 - sum) < val)) ||
-        ((sum <  0) && ((fMin128 - sum) > val)))
-    {
-        string errStr = "SUM(int128_t)";
-        errStr = IDBErrorInfo::instance()->errorMsg(ERR_WF_OVERFLOW, errStr);
-        cerr << errStr << endl;
-        throw IDBExcept(errStr, ERR_WF_OVERFLOW);
-    }
+    datatypes::AdditionOverflowCheck ofCheckOp;
+    ofCheckOp(sum, val);
 }
 
-template<typename T_IN, typename T_OUT>
-inline void WF_sum_avg<T_IN, T_OUT>::checkSumLimit(uint128_t val, uint128_t sum)
-{
-    if ((fMaxu128 - sum) < val)
-    {
-        string errStr = "SUM(uint128_t)";
-        errStr = IDBErrorInfo::instance()->errorMsg(ERR_WF_OVERFLOW, errStr);
-        cerr << errStr << endl;
-        throw IDBExcept(errStr, ERR_WF_OVERFLOW);
-    }
-}
+template<>
+inline void WF_sum_avg<long double,long double>::checkSumLimit(long double& val, long double& sum)
+{ }
+
+template<>
+inline void WF_sum_avg<float, long double>::checkSumLimit(float&, long double&)
+{ }
+
+template<>
+inline void WF_sum_avg<long, long double>::checkSumLimit(long&, long double&)
+{ }
+
+template<>
+inline void WF_sum_avg<unsigned long, long double>::checkSumLimit(unsigned long&, long double&)
+{ }
+template<>
+inline void WF_sum_avg<double, long double>::checkSumLimit(double&, long double&)
+{ }
+
+template<>
+void WF_sum_avg<int128_t,int128_t>::checkSumLimit(int128_t& val, int128_t& sum);
+template<>
+void WF_sum_avg<long double,long double>::checkSumLimit(long double& val, long double& sum);
+template<>
+void WF_sum_avg<float, long double>::checkSumLimit(float&, long double&);
+template<>
+void WF_sum_avg<long, long double>::checkSumLimit(long&, long double&);
+template<>
+void WF_sum_avg<unsigned long, long double>::checkSumLimit(unsigned long&, long double&);
+template<>
+void WF_sum_avg<double, long double>::checkSumLimit(double&, long double&);
 
 template<typename T_IN, typename T_OUT>
 int128_t WF_sum_avg<T_IN, T_OUT>::calculateAvg(int128_t sum, uint64_t count, int scale)
@@ -118,41 +132,6 @@ int128_t WF_sum_avg<T_IN, T_OUT>::calculateAvg(int128_t sum, uint64_t count, int
     return avg;
 }
 
-template<typename T_IN, typename T_OUT>
-uint128_t WF_sum_avg<T_IN, T_OUT>::calculateAvg(uint128_t sum, uint64_t count, int scale)
-{
-    uint128_t avg = 0;
-    uint128_t factor;
-    datatypes::getScaleDivisor(factor, scale);
-    if (scale > 0)
-    {
-        if ((sum * factor) / factor == sum)
-        {
-            avg = sum * factor;
-            avg /= count;
-        }
-        else
-        {
-            // scale won't fit before divide, we're gonna lose precision.
-            avg = sum / count;
-            if ((avg * factor) / factor != avg) // Still won't fit
-            {
-                string errStr = string("AVG(int)");
-                errStr = IDBErrorInfo::instance()->errorMsg(ERR_WF_OVERFLOW, errStr);
-                cerr << errStr << endl;
-                throw IDBExcept(errStr, ERR_WF_OVERFLOW);
-            }
-            avg *= factor;
-        }
-    }
-    else
-    {
-        avg = sum / count;
-    }
-    avg += 0.5;
-    return avg;
-}
-
 template<typename T_IN, typename T_OUT>
 inline long double WF_sum_avg<T_IN, T_OUT>::calculateAvg(long double sum, uint64_t count, int scale)
 {
@@ -188,31 +167,19 @@ boost::shared_ptr<WindowFunctionType> WF_sum_avg<T_IN, T_OUT>::makeFunction(int
         }
 
         case CalpontSystemCatalog::DECIMAL:
+        case CalpontSystemCatalog::UDECIMAL:
         {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
+            if (wc->functionParms()[0]->resultType().colWidth < datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_sum_avg<int64_t, int128_t>(id, name));
             }
-            else
+            else if (wc->functionParms()[0]->resultType().colWidth == datatypes::MAXDECIMALWIDTH)
             {
                 func.reset(new WF_sum_avg<int128_t, int128_t>(id, name));
             }
             break;
         }
         
-        case CalpontSystemCatalog::UDECIMAL:
-        {
-            if (wc->functionParms()[0]->resultType().colWidth < 16)
-            {
-                func.reset(new WF_sum_avg<uint64_t, uint128_t>(id, name));
-            }
-            else
-            {
-                func.reset(new WF_sum_avg<uint128_t, uint128_t>(id, name));
-            }
-            break;
-        }
-
         case CalpontSystemCatalog::DOUBLE:
         case CalpontSystemCatalog::UDOUBLE:
         {
diff --git a/utils/windowfunction/wf_sum_avg.h b/utils/windowfunction/wf_sum_avg.h
index b86a9c16d..6ecc37314 100644
--- a/utils/windowfunction/wf_sum_avg.h
+++ b/utils/windowfunction/wf_sum_avg.h
@@ -39,9 +39,6 @@ public:
         WindowFunctionType(id, name), fDistinct(id != WF__SUM && id != WF__AVG)
     {
         resetData();
-        utils::int128Max(fMax128);
-        utils::int128Min(fMin128);
-        utils::uint128Max(fMaxu128);
     }
 
     // pure virtual in base
@@ -58,19 +55,17 @@ protected:
     uint64_t    fCount;
     bool        fDistinct;
     std::set<T_IN> fSet;
-    int128_t    fMax128;
-    int128_t    fMin128;
-    uint128_t   fMaxu128;
 
-    void checkSumLimit(long double val, long double sum);
-    void checkSumLimit(int128_t val, int128_t sum);
-    void checkSumLimit(uint128_t val, uint128_t sum);
-    
+    void checkSumLimit(T_IN& val, T_OUT& sum);
+
     int128_t calculateAvg(int128_t sum, uint64_t count, int scale);
-    uint128_t calculateAvg(uint128_t sum, uint64_t count, int scale);
     long double calculateAvg(long double sum, uint64_t count, int scale);
 };
 
+template<>
+void WF_sum_avg<long double,long double>::checkSumLimit(long double& val, long double& sum);
+
+
 } // namespace
 
 #endif  // UTILS_WF_SUM_AVG_H
diff --git a/writeengine/server/we_dmlcommandproc.cpp b/writeengine/server/we_dmlcommandproc.cpp
index dbbc5162c..0a17d5128 100644
--- a/writeengine/server/we_dmlcommandproc.cpp
+++ b/writeengine/server/we_dmlcommandproc.cpp
@@ -423,7 +423,7 @@ uint8_t WE_DMLCommandProc::processSingleInsert(messageqcpp::ByteStream& bs, std:
 
     // call the write engine to write the rows
     int error = NO_ERROR;
-    // WIP
+    // MCOL-641 WIP
     fWEWrapper.setDebugLevel(WriteEngine::DEBUG_3);
     cout << "inserting a row with transaction id " << txnid.id << endl;
     fWEWrapper.setIsInsert(true);