diff --git a/graph/Graph.cc b/graph/Graph.cc
index 66cbc395..936f6d2b 100644
--- a/graph/Graph.cc
+++ b/graph/Graph.cc
@@ -520,6 +520,26 @@ Graph::arrivals(Vertex *vertex)
   return arrivals_.pointer(vertex->arrivals());
 }
 
+Required *
+Graph::makeRequireds(Vertex *vertex,
+                     uint32_t count)
+{
+  Required *requireds;
+  ArrivalId id;
+  {
+    UniqueLock lock(arrivals_lock_);
+    arrivals_.make(count, requireds, id);
+  }
+  vertex->setRequireds(id);
+  return requireds;
+}
+
+Required *
+Graph::requireds(Vertex *vertex)
+{
+  return arrivals_.pointer(vertex->requireds());
+}
+
 void
 Graph::clearArrivals()
 {
@@ -1025,8 +1045,8 @@ Vertex::init(Pin *pin,
   in_edges_ = edge_id_null;
   out_edges_ = edge_id_null;
   arrivals_ = arrival_null;
+  requireds_ = arrival_null;
   prev_paths_ = prev_path_null;
-  has_requireds_ = false;
   tag_group_index_ = tag_group_index_max;
   slew_annotated_ = false;
   sim_value_ = unsigned(LogicValue::unknown);
@@ -1157,25 +1177,31 @@ Vertex::setArrivals(ArrivalId id)
   arrivals_ = id;
 }
 
+void
+Vertex::setRequireds(ArrivalId id)
+{
+  requireds_ = id;
+}
+
+void
+Vertex::deleteRequireds()
+{
+  requireds_ = arrival_null;
+}
+
 void
 Vertex::setPrevPaths(PrevPathId prev_paths)
 {
   prev_paths_ = prev_paths;
 }
 
-void
-Vertex::setHasRequireds(bool has_req)
-{
-  has_requireds_ = has_req;
-}
-
 void
 Vertex::deletePaths()
 {
   arrivals_ = arrival_null;
+  requireds_ = arrival_null;
   prev_paths_ = prev_path_null;
   tag_group_index_ = tag_group_index_max;
-  has_requireds_ = false;
   crpr_path_pruning_disabled_ = false;
 }
 
diff --git a/include/sta/Graph.hh b/include/sta/Graph.hh
index b6bc9876..70ed6a02 100644
--- a/include/sta/Graph.hh
+++ b/include/sta/Graph.hh
@@ -101,7 +101,11 @@ public:
   Arrival *makeArrivals(Vertex *vertex,
 			uint32_t count);
   Arrival *arrivals(Vertex *vertex);
+  Required *makeRequireds(Vertex *vertex,
+                          uint32_t count);
+  Required *requireds(Vertex *vertex);
   void clearArrivals();
+  size_t arrivalCount() const { return arrivals_.size(); }
   PathVertexRep *makePrevPaths(Vertex *vertex,
 			       uint32_t count);
   PathVertexRep *prevPaths(Vertex *vertex) const;
@@ -278,11 +282,11 @@ public:
   LevelColor color() const { return static_cast<LevelColor>(color_); }
   void setColor(LevelColor color);
   ArrivalId arrivals() { return arrivals_; }
+  ArrivalId requireds() { return requireds_; }
+  bool hasRequireds() const { return requireds_ != arrival_null; }
+  void deleteRequireds();
   PrevPathId prevPaths() const { return prev_paths_; }
   void setPrevPaths(PrevPathId id);
-  // Requireds optionally follow arrivals in the same array.
-  bool hasRequireds() const { return has_requireds_; }
-  void setHasRequireds(bool has_req);
   TagGroupIndex tagGroupIndex() const;
   void setTagGroupIndex(TagGroupIndex tag_index);
   // Slew is annotated by sdc set_annotated_transition cmd.
@@ -337,9 +341,11 @@ protected:
 	    bool is_bidirect_drvr,
 	    bool is_reg_clk);
   void setArrivals(ArrivalId id);
+  void setRequireds(ArrivalId id);
 
   Pin *pin_;
   ArrivalId arrivals_;
+  ArrivalId requireds_;
   PrevPathId prev_paths_;
   EdgeId in_edges_;		// Edges to this vertex.
   EdgeId out_edges_;		// Edges from this vertex.
@@ -357,7 +363,6 @@ protected:
   unsigned color_:2;
   // LogicValue gcc barfs if this is dcl'd.
   unsigned sim_value_:3;
-  bool has_requireds_:1;
   // Bidirect pins have two vertices.
   // This flag distinguishes the driver and load vertices.
   bool is_bidirect_drvr_:1;
diff --git a/search/PathVertex.cc b/search/PathVertex.cc
index 88e49bab..cf1355b4 100644
--- a/search/PathVertex.cc
+++ b/search/PathVertex.cc
@@ -245,15 +245,12 @@ PathVertex::setArrival(Arrival arrival,
 const Required &
 PathVertex::required(const StaState *sta) const
 {
-  if (tag_ && vertex_->hasRequireds()) {
-    const Search *search = sta->search();
-    TagGroup *tag_group = search->tagGroup(vertex_);
-    int req_index = tag_group->requiredIndex(arrival_index_);
-    Arrival *arrivals = sta->graph()->arrivals(vertex_);
-    return arrivals[req_index];
+  if (tag_) {
+    Required *requireds = sta->graph()->requireds(vertex_);
+    if (requireds)
+      return requireds[arrival_index_];
   }
-  else
-    return delayInitValue(minMax(sta)->opposite());
+  return delayInitValue(minMax(sta)->opposite());
 }
 
 void
@@ -261,27 +258,21 @@ PathVertex::setRequired(const Required &required,
 			const StaState *sta)
 {
   Graph *graph = sta->graph();
-  const Search *search = sta->search();
-  TagGroup *tag_group = search->tagGroup(vertex_);
-  Arrival *arrivals = graph->arrivals(vertex_);
-  int arrival_count = tag_group->arrivalCount();
-  if (!vertex_->hasRequireds()) {
-    Arrival *new_arrivals = graph->makeArrivals(vertex_, arrival_count * 2);
-    for (int i = 0; i < arrival_count; i++)
-      new_arrivals[i] =arrivals[i];
-    vertex_->setHasRequireds(true);
-    arrivals = new_arrivals;
+  Required *requireds = graph->requireds(vertex_);
+  if (requireds == nullptr) {
+    const Search *search = sta->search();
+    TagGroup *tag_group = search->tagGroup(vertex_);
+    int arrival_count = tag_group->arrivalCount();
+    requireds = graph->makeRequireds(vertex_, arrival_count);
   }
-  int req_index = arrival_index_ + arrival_count;
-  arrivals[req_index] = required;
+  requireds[arrival_index_] = required;
 }
 
 void
 PathVertex::deleteRequireds(Vertex *vertex,
 			    const StaState *)
 {
-  vertex->setHasRequireds(false);
-  // Don't bother reclaiming requieds from arrival table.
+  vertex->deleteRequireds();
 }
 
 bool
diff --git a/search/Search.cc b/search/Search.cc
index cd380f19..a8f4f564 100644
--- a/search/Search.cc
+++ b/search/Search.cc
@@ -2685,10 +2685,7 @@ Search::setVertexArrivals(Vertex *vertex,
     bool has_requireds = vertex->hasRequireds();
     // Reuse arrival array if it is the same size.
     if (prev_tag_group
-	&& arrival_count == prev_tag_group->arrivalCount()
-	&& (!has_requireds
-	    // Requireds can only be reused if the tag group is unchanged.
-	    || tag_group == prev_tag_group)) {
+	&& arrival_count == prev_tag_group->arrivalCount()) {
       if  (tag_bldr->hasClkTag() || tag_bldr->hasGenClkSrcTag()) {
 	if (prev_paths == nullptr)
 	  prev_paths = graph_->makePrevPaths(vertex, arrival_count);
@@ -2700,6 +2697,13 @@ Search::setVertexArrivals(Vertex *vertex,
       }
       tag_bldr->copyArrivals(tag_group, prev_arrivals, prev_paths);
       vertex->setTagGroupIndex(tag_group->index());
+
+      if (has_requireds) {
+	requiredInvalid(vertex);
+        if (tag_group != prev_tag_group)
+          // Requireds can only be reused if the tag group is unchanged.
+          vertex->deleteRequireds();
+      }
     }
     else {
       Arrival *arrivals = graph_->makeArrivals(vertex, arrival_count);
@@ -2712,7 +2716,7 @@ Search::setVertexArrivals(Vertex *vertex,
 
       if (has_requireds) {
 	requiredInvalid(vertex);
-	vertex->setHasRequireds(false);
+	vertex->deleteRequireds();
       }
     }
   }
@@ -2724,6 +2728,7 @@ Search::reportArrivals(Vertex *vertex) const
   report_->reportLine("Vertex %s", vertex->name(sdc_network_));
   TagGroup *tag_group = tagGroup(vertex);
   Arrival *arrivals = graph_->arrivals(vertex);
+  Required *requireds = graph_->requireds(vertex);
   if (tag_group) {
     report_->reportLine("Group %u", tag_group->index());
     ArrivalMap::Iterator arrival_iter(tag_group->arrivalMap());
@@ -2734,13 +2739,8 @@ Search::reportArrivals(Vertex *vertex) const
       PathAnalysisPt *path_ap = tag->pathAnalysisPt(this);
       const RiseFall *rf = tag->transition();
       const char *req = "?";
-      if (vertex->hasRequireds()) {
-	int req_index;
-	bool exists;
-	tag_group->requiredIndex(tag, req_index, exists);
-	if (exists)
-	  req = delayAsString(arrivals[req_index], this);
-      }
+      if (requireds)
+        req = delayAsString(requireds[arrival_index], this);
       bool report_clk_prev = false;
       const char *clk_prev = "";
       if (report_clk_prev
diff --git a/search/TagGroup.cc b/search/TagGroup.cc
index 7b015bd0..fcc230a3 100644
--- a/search/TagGroup.cc
+++ b/search/TagGroup.cc
@@ -86,22 +86,6 @@ TagGroup::arrivalIndex(Tag *tag,
   arrival_map_->findKey(tag, arrival_index, exists);
 }
 
-void
-TagGroup::requiredIndex(Tag *tag,
-			int &req_index,
-			bool &exists) const
-{
-  arrivalIndex(tag, req_index, exists);
-  if (exists)
-    req_index += arrivalCount();
-}
-
-int
-TagGroup::requiredIndex(int arrival_index) const
-{
-  return arrival_index + arrivalCount();
-}
-
 void
 TagGroup::report(const StaState *sta) const
 {
diff --git a/search/TagGroup.hh b/search/TagGroup.hh
index b08ac3ec..5d723779 100644
--- a/search/TagGroup.hh
+++ b/search/TagGroup.hh
@@ -57,10 +57,6 @@ public:
   void arrivalIndex(Tag *tag,
 		    int &arrival_index,
 		    bool &exists) const;
-  void requiredIndex(Tag *tag,
-		     int &req_index,
-		     bool &exists) const;
-  int requiredIndex(int arrival_index) const;
   ArrivalMap *arrivalMap() const { return arrival_map_; }
   bool hasTag(Tag *tag) const;
 
diff --git a/tcl/StaTcl.i b/tcl/StaTcl.i
index a05b966a..3fe2e0a4 100644
--- a/tcl/StaTcl.i
+++ b/tcl/StaTcl.i
@@ -5301,6 +5301,12 @@ arrival_count()
   return Sta::sta()->arrivalCount();
 }
 
+int
+graph_arrival_count()
+{
+  return Sta::sta()->graph()->arrivalCount();
+}
+
 void
 delete_all_memory()
 {