diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7622bf90..8e0fa284 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,7 +24,7 @@ if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.14)
 cmake_policy(SET CMP0086 NEW)
 endif()
 
-project(STA VERSION 2.3.0
+project(STA VERSION 2.3.1
   LANGUAGES CXX
 )
 
diff --git a/doc/ChangeLog.txt b/doc/ChangeLog.txt
index 0451c28b..14f7d923 100644
--- a/doc/ChangeLog.txt
+++ b/doc/ChangeLog.txt
@@ -3,6 +3,13 @@ OpenSTA Timing Analyzer Release Notes
 
 This file summarizes user visible changes for each release.
 
+Release 2.3.1 2020/11/08
+-------------------------
+
+The read_sdf command no longer supports the -analysis_type, -type, -min_type,
+and -max_type arguments. Use the set_operating_conditions -analysis_type
+command to set the analysis type before read_sdf.
+
 Release 2.2.0 2020/07/18
 -------------------------
 
diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index e1f378c6..2953e6b6 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index 0346b2a7..fd779d57 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/sdf/Sdf.i b/sdf/Sdf.i
index d5ebdf61..02782602 100644
--- a/sdf/Sdf.i
+++ b/sdf/Sdf.i
@@ -30,8 +30,7 @@ using sta::AnalysisType;
 using sta::MinMax;
 using sta::MinMaxAllNull;
 using sta::stringEq;
-using sta::readSdfSingle;
-using sta::readSdfMinMax;
+using sta::readSdf;
 using sta::reportAnnotatedDelay;
 using sta::reportAnnotatedCheck;
 
@@ -39,62 +38,27 @@ using sta::reportAnnotatedCheck;
 
 %inline %{
 
-// min/max index is:
-//  sdf_min = 0
-//  sdf_typ = 1
-//  sdf_max = 2
-
 // If unescaped_dividers is true path names do not have to escape
 // hierarchy dividers when the path name is quoted.
 // For example verilog "\mod1/mod2 " can be referenced as "mod1/mod2"
 // instead of the correct "mod1\/mod2".
 
-// Read sdf_index value from sdf triples.
 // Return true if successful.
 bool
-read_sdf_file_single(const char *filename,
-		     const char *path,
-		     Corner *corner,
-		     int sdf_index,
-		     AnalysisType analysis_type,
-		     bool unescaped_dividers,
-		     bool incremental_only,
-		     MinMaxAllNull *cond_use)
+read_sdf_file(const char *filename,
+              const char *path,
+              Corner *corner,
+              bool unescaped_dividers,
+              bool incremental_only,
+              MinMaxAllNull *cond_use)
 {
   cmdLinkedNetwork();
   Sta *sta = Sta::sta();
   sta->ensureGraph();
   if (stringEq(path, ""))
     path = NULL;
-  bool success = readSdfSingle(filename, path, corner, sdf_index,
-			       analysis_type, unescaped_dividers,
-			       incremental_only, cond_use, sta);
-  sta->search()->arrivalsInvalid();
-  return success;
-}
-
-// Read sdf_min_index and sdf_max_index values from sdf triples.
-// Return true if successful.
-bool
-read_sdf_file_min_max(const char *filename,
-		      const char *path,
-		      Corner *corner,
-		      int sdf_min_index,
-		      int sdf_max_index,
-		      AnalysisType analysis_type,
-		      bool unescaped_dividers,
-		      bool incremental_only,
-		      MinMaxAllNull *cond_use)
-{
-  cmdLinkedNetwork();
-  Sta *sta = Sta::sta();
-  sta->ensureGraph();
-  if (stringEq(path, ""))
-    path = NULL;
-  bool success = readSdfMinMax(filename, path, corner, sdf_min_index,
-			       sdf_max_index, analysis_type,
-			       unescaped_dividers, incremental_only,
-			       cond_use, sta);
+  bool success = readSdf(filename, path, corner, unescaped_dividers, incremental_only,
+                         cond_use, sta);
   sta->search()->arrivalsInvalid();
   return success;
 }
diff --git a/sdf/Sdf.tcl b/sdf/Sdf.tcl
index 7130569c..1cd1c89c 100644
--- a/sdf/Sdf.tcl
+++ b/sdf/Sdf.tcl
@@ -18,17 +18,14 @@ namespace eval sta {
 
 define_cmd_args "read_sdf" \
   {[-path path] [-corner corner_name]\
-     [-analysis_type single|bc_wc|on_chip_variation]\
-     [-type sdf_min|sdf_typ|sdf_max]\
-     [-min_type sdf_min|sdf_typ|sdf_max]\
-     [-max_type sdf_min|sdf_typ|sdf_max]\
      [-cond_use min|max|min_max]\
      [-unescaped_dividers] filename}
 
 proc_redirect read_sdf {
   parse_key_args "read_sdf" args \
-    keys {-path -corner -analysis_type -type -min_type -max_type -cond_use} \
+    keys {-path -corner -cond_use -analysis_type} \
     flags {-unescaped_dividers -incremental_only}
+
   check_argc_eq1 "read_sdf" $args
   set filename [file nativename [lindex $args 0]]
   set path ""
@@ -36,17 +33,6 @@ proc_redirect read_sdf {
     set path $keys(-path)
   }
   set corner [parse_corner keys]
-  if [info exists keys(-analysis_type)] {
-    set analysis_type $keys(-analysis_type)
-    if { $analysis_type == "single" \
-	   || $analysis_type == "bc_wc" \
-	   || $analysis_type == "on_chip_variation" } {
-      # -analysis_type is an implicit set_operating_conditions
-      set_analysis_type_cmd $analysis_type
-    } else {
-      sta_error 429 "-analysis_type must be single, bc_wc or on_chip_variation"
-    }
-  }
 
   set cond_use "NULL"
   if [info exists keys(-cond_use)] {
@@ -60,53 +46,14 @@ proc_redirect read_sdf {
       sta_error 430 "-cond_use min_max cannot be used with analysis type single."
     }
   }
+  if [info exists keys(-analysis_type)] {
+    sta_warn 617 "-analysis_type is deprecated. Use set_operating_conditions -analysis_type."
+  }
 
   set unescaped_dividers [info exists flags(-unescaped_dividers)]
-  set analysis_type [operating_condition_analysis_type]
   set incremental_only [info exists flags(-incremental_only)]
-  if { $analysis_type == "single" } {
-    # default sdf_max
-    set index 2
-    if [info exists keys(-type)] {
-      set index [parse_sdf_index "-type" $keys(-type)]
-    }
-    if [info exists keys(-min_type)] {
-      sta_warn 613 "-min_type ignored by analysis_type single."
-    }
-    if [info exists keys(-max_type)] {
-      sta_warn 614 "-max_type ignored by analysis_type single."
-    }
-    read_sdf_file_single $filename $path $corner $index $analysis_type \
-      $unescaped_dividers $incremental_only $cond_use
-  } elseif { $analysis_type == "bc_wc" \
-	       || $analysis_type == "on_chip_variation" } {
-    # default sdf_min, sdf_max
-    set min_index 0
-    set max_index 2
-    if [info exists keys(-min_type)] {
-      set min_index [parse_sdf_index "-min_type" $keys(-min_type)]
-    }
-    if [info exists keys(-max_type)] {
-      set max_index [parse_sdf_index "-max_type" $keys(-max_type)]
-    }
-    if [info exists keys(-type)] {
-      sta_warn 615 "-type ignored by analysis_type $analysis_type."
-    }
-    read_sdf_file_min_max $filename $path $corner $min_index $max_index \
-      $analysis_type $unescaped_dividers $incremental_only $cond_use
-  }
-}
-
-proc parse_sdf_index { key index } {
-  if { $index == "sdf_min" } {
-    return 0
-  } elseif { $index == "sdf_typ" } {
-    return 1
-  } elseif { $index == "sdf_max" } {
-    return 2
-  } else {
-    sta_error 431 "$key must be sdf_min, sdf_typ, or sdf_max."
-  }
+  read_sdf_file $filename $path $corner $unescaped_dividers \
+    $incremental_only $cond_use
 }
 
 ################################################################
diff --git a/sdf/SdfLex.ll b/sdf/SdfLex.ll
index 4d9947cf..401b3071 100644
--- a/sdf/SdfLex.ll
+++ b/sdf/SdfLex.ll
@@ -17,7 +17,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "util/FlexDisableRegister.hh"
-#include "sdf/Sdf.hh"
+#include "sdf/SdfReaderPvt.hh"
 #include "SdfParse.hh"
 
 #define YY_NO_INPUT
diff --git a/sdf/SdfParse.yy b/sdf/SdfParse.yy
index a2e37297..91983ff7 100644
--- a/sdf/SdfParse.yy
+++ b/sdf/SdfParse.yy
@@ -18,7 +18,7 @@
 
 #include <ctype.h>
 
-#include "sdf/Sdf.hh"
+#include "sdf/SdfReaderPvt.hh"
 
 int SdfLex_lex();
 #define SdfParse_lex SdfLex_lex
diff --git a/sdf/SdfReader.cc b/sdf/SdfReader.cc
index 97b5416b..c9adff15 100644
--- a/sdf/SdfReader.cc
+++ b/sdf/SdfReader.cc
@@ -29,7 +29,8 @@
 #include "Graph.hh"
 #include "Corner.hh"
 #include "DcalcAnalysisPt.hh"
-#include "sdf/Sdf.hh"
+#include "Sdc.hh"
+#include "sdf/SdfReaderPvt.hh"
 
 extern int
 SdfParse_parse();
@@ -79,43 +80,20 @@ private:
 SdfReader *sdf_reader = nullptr;
 
 bool
-readSdfSingle(const char *filename,
-	      const char *path,
-	      Corner *corner,
-	      int sdf_index,
-              AnalysisType analysis_type,
-	      bool unescaped_dividers,
-	      bool incremental_only,
-	      MinMaxAll *cond_use,
-	      StaState *sta)
-{
-  int arc_index = corner->findDcalcAnalysisPt(MinMax::max())->index();
-  SdfReader reader(filename, path, arc_index, sdf_index,
-                   SdfReader::nullIndex(), SdfReader::nullIndex(),
-                   analysis_type, unescaped_dividers, incremental_only,
-		   cond_use, sta);
-  sdf_reader = &reader;
-  return reader.read();
-}
-
-bool
-readSdfMinMax(const char *filename,
-	      const char *path,
-	      Corner *corner,
-	      int sdf_min_index,
-	      int sdf_max_index,
-	      AnalysisType analysis_type,
-	      bool unescaped_dividers,
-	      bool incremental_only,
-	      MinMaxAll *cond_use,
-	      StaState *sta)
+readSdf(const char *filename,
+        const char *path,
+        Corner *corner,
+        bool unescaped_dividers,
+        bool incremental_only,
+        MinMaxAll *cond_use,
+        StaState *sta)
 {
   int arc_min_index = corner->findDcalcAnalysisPt(MinMax::min())->index();
   int arc_max_index = corner->findDcalcAnalysisPt(MinMax::max())->index();
   SdfReader reader(filename, path,
-		   arc_min_index, sdf_min_index,
-		   arc_max_index, sdf_max_index,
-		   analysis_type, unescaped_dividers, incremental_only,
+		   arc_min_index, arc_max_index, 
+		   sta->sdc()->analysisType(),
+                   unescaped_dividers, incremental_only,
 		   cond_use, sta);
   sdf_reader = &reader;
   return reader.read();
@@ -124,9 +102,7 @@ readSdfMinMax(const char *filename,
 SdfReader::SdfReader(const char *filename,
 		     const char *path,
                      int arc_min_index,
-		     int triple_min_index,
 		     int arc_max_index,
-		     int triple_max_index,
 		     AnalysisType analysis_type,
 		     bool unescaped_dividers,
 		     bool is_incremental_only,
@@ -135,8 +111,8 @@ SdfReader::SdfReader(const char *filename,
   StaState(sta),
   filename_(filename),
   path_(path),
-  triple_min_index_(triple_min_index),
-  triple_max_index_(triple_max_index),
+  triple_min_index_(0),
+  triple_max_index_(2),
   arc_delay_min_index_(arc_min_index),
   arc_delay_max_index_(arc_max_index),
   analysis_type_(analysis_type),
@@ -475,28 +451,25 @@ SdfReader::timingCheck1(TimingRole *role,
       Pin *data_pin = network_->findPin(instance_, data_port_name);
       Pin *clk_pin = network_->findPin(instance_, clk_port_name);
       if (data_pin && clk_pin) {
-	// Hack to match PT; always use triple max value for check.
-	if (triple_min_index_ != null_index_
-	    && triple_max_index_ != null_index_) {
-	  float **values = triple->values();
-	  float *value_min = values[triple_min_index_];
-	  float *value_max = values[triple_max_index_];
-          if (value_min && value_max) {
-	    switch (analysis_type_) {
-	    case AnalysisType::single:
-	      break;
-	    case AnalysisType::bc_wc:
-	      if (role->genericRole() == TimingRole::setup())
-		*value_min = *value_max;
-	      else
-		*value_max = *value_min;
-	      break;
-	    case AnalysisType::ocv:
-	      *value_min = *value_max;
-	      break;
-	    }
-	  }
-	}
+	// Hack: always use triple max value for check.
+        float **values = triple->values();
+        float *value_min = values[triple_min_index_];
+        float *value_max = values[triple_max_index_];
+        if (value_min && value_max) {
+          switch (analysis_type_) {
+          case AnalysisType::single:
+            break;
+          case AnalysisType::bc_wc:
+            if (role->genericRole() == TimingRole::setup())
+              *value_min = *value_max;
+            else
+              *value_max = *value_min;
+            break;
+          case AnalysisType::ocv:
+            *value_min = *value_max;
+            break;
+          }
+        }
 	bool matched = annotateCheckEdges(data_pin, data_edge,
 					  clk_pin, clk_edge, role,
 					  triple, false);
@@ -769,12 +742,8 @@ SdfReader::setEdgeArcDelaysCondUse(Edge *edge,
 				   SdfTriple *triple)
 {
   float **values = triple->values();
-  float *value_min = nullptr;
-  if (triple_min_index_ != null_index_)
-    value_min = values[triple_min_index_];
-  float *value_max = nullptr;
-  if (triple_max_index_ != null_index_)
-    value_max = values[triple_max_index_];
+  float *value_min = values[triple_min_index_];
+  float *value_max = value_max = values[triple_max_index_];
   MinMax *min, *max;
   if (cond_use_ == MinMaxAll::min()) {
     min = MinMax::min();
diff --git a/sdf/SdfReader.hh b/sdf/SdfReader.hh
index 2a15a87f..2c6cced6 100644
--- a/sdf/SdfReader.hh
+++ b/sdf/SdfReader.hh
@@ -53,29 +53,13 @@ class StaState;
 // conditions and the maximum of the conditional delay values is used for
 // maximum operating conditions.
 
-// Read sdf_index value from sdf triples.
 bool
-readSdfSingle(const char *filename,
-	      const char *path,
-              Corner *corner,
-	      int sdf_index,
-	      AnalysisType analysis_type,
-	      bool unescaped_dividers,
-	      bool incremental_only,
-              MinMaxAll *cond_use,
-	      StaState *sta);
-
-// Read sdf_min_index and sdf_max_index values from sdf triples.
-bool
-readSdfMinMax(const char *filename,
-	      const char *path,
-	      Corner *corner,
-              int sdf_min_index,
-	      int sdf_max_index,
-	      AnalysisType analysis_type,
-	      bool unescaped_dividers,
-	      bool incremental_only,
-              MinMaxAll *cond_use,
-	      StaState *sta);
+readSdf(const char *filename,
+        const char *path,
+        Corner *corner,
+        bool unescaped_dividers,
+        bool incremental_only,
+        MinMaxAll *cond_use,
+        StaState *sta);
 
 } // namespace
diff --git a/sdf/Sdf.hh b/sdf/SdfReaderPvt.hh
similarity index 97%
rename from sdf/Sdf.hh
rename to sdf/SdfReaderPvt.hh
index e9ad6fc2..b8b5af5e 100644
--- a/sdf/Sdf.hh
+++ b/sdf/SdfReaderPvt.hh
@@ -50,9 +50,7 @@ public:
   SdfReader(const char *filename,
 	    const char *path,
 	    int arc_min_index,
-	    int triple_min_index,
 	    int arc_max_index,
-	    int triple_max_index,
 	    AnalysisType analysis_type,
 	    bool unescaped_dividers,
 	    bool is_incremental_only,
@@ -60,8 +58,6 @@ public:
 	    StaState *sta);
   ~SdfReader();
   bool read();
-  // Arc/Triple index passed to read() to ignore arg.
-  static int nullIndex() { return null_index_; }
 
   void setDivider(char divider);
   void setTimescale(float multiplier, const char *units);