Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -3890,21 +3890,20 @@
     p->a[0].fg.jointype = 0;
   }
 }
 
 /*
-** Begin a transaction
+** Generate VDBE code for a BEGIN statement.
 */
 void sqlite3BeginTransaction(Parse *pParse, int type){
   sqlite3 *db;
   Vdbe *v;
   int i;
 
   assert( pParse!=0 );
   db = pParse->db;
   assert( db!=0 );
-/*  if( db->aDb[0].pBt==0 ) return; */
   if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "BEGIN", 0, 0) ){
     return;
   }
   v = sqlite3GetVdbe(pParse);
   if( !v ) return;
@@ -3912,15 +3911,15 @@
     for(i=0; i<db->nDb; i++){
       sqlite3VdbeAddOp2(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1);
       sqlite3VdbeUsesBtree(v, i);
     }
   }
-  sqlite3VdbeAddOp2(v, OP_AutoCommit, 0, 0);
+  sqlite3VdbeAddOp0(v, OP_AutoCommit);
 }
 
 /*
-** Commit a transaction
+** Generate VDBE code for a COMMIT statement.
 */
 void sqlite3CommitTransaction(Parse *pParse){
   Vdbe *v;
 
   assert( pParse!=0 );
@@ -3928,16 +3927,16 @@
   if( sqlite3AuthCheck(pParse, SQLITE_TRANSACTION, "COMMIT", 0, 0) ){
     return;
   }
   v = sqlite3GetVdbe(pParse);
   if( v ){
-    sqlite3VdbeAddOp2(v, OP_AutoCommit, 1, 0);
+    sqlite3VdbeAddOp1(v, OP_AutoCommit, 1);
   }
 }
 
 /*
-** Rollback a transaction
+** Generate VDBE code for a ROLLBACK statement.
 */
 void sqlite3RollbackTransaction(Parse *pParse){
   Vdbe *v;
 
   assert( pParse!=0 );

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -3006,32 +3006,31 @@
 ** This instruction causes the VM to halt.
 */
 case OP_AutoCommit: {
   int desiredAutoCommit;
   int iRollback;
-  int turnOnAC;
 
   desiredAutoCommit = pOp->p1;
   iRollback = pOp->p2;
-  turnOnAC = desiredAutoCommit && !db->autoCommit;
   assert( desiredAutoCommit==1 || desiredAutoCommit==0 );
   assert( desiredAutoCommit==1 || iRollback==0 );
   assert( db->nVdbeActive>0 );  /* At least this one VM is active */
   assert( p->bIsReader );
 
-  if( turnOnAC && !iRollback && db->nVdbeWrite>0 ){
-    /* If this instruction implements a COMMIT and other VMs are writing
-    ** return an error indicating that the other VMs must complete first. 
-    */
-    sqlite3VdbeError(p, "cannot commit transaction - "
-                        "SQL statements in progress");
-    rc = SQLITE_BUSY;
-  }else if( desiredAutoCommit!=db->autoCommit ){
+  if( desiredAutoCommit!=db->autoCommit ){
     if( iRollback ){
       assert( desiredAutoCommit==1 );
       sqlite3RollbackAll(db, SQLITE_ABORT_ROLLBACK);
       db->autoCommit = 1;
+    }else if( desiredAutoCommit && db->nVdbeWrite>0 ){
+      /* If this instruction implements a COMMIT and other VMs are writing
+      ** return an error indicating that the other VMs must complete first. 
+      */
+      sqlite3VdbeError(p, "cannot commit transaction - "
+                          "SQL statements in progress");
+      rc = SQLITE_BUSY;
+      break;
     }else if( (rc = sqlite3VdbeCheckFk(p, 1))!=SQLITE_OK ){
       goto vdbe_return;
     }else{
       db->autoCommit = (u8)desiredAutoCommit;
     }

Index: src/vdbeaux.c
==================================================================
--- src/vdbeaux.c
+++ src/vdbeaux.c
@@ -532,11 +532,11 @@
   p->readOnly = 1;
   p->bIsReader = 0;
   for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
     u8 opcode = pOp->opcode;
 
-    /* NOTE: Be sure to update mkopcodeh.awk when adding or removing
+    /* NOTE: Be sure to update mkopcodeh.tcl when adding or removing
     ** cases from this switch! */
     switch( opcode ){
       case OP_Transaction: {
         if( pOp->p2!=0 ) p->readOnly = 0;
         /* fall thru */