Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -3906,11 +3906,11 @@
   }
   v = sqlite3GetVdbe(pParse);
   if( !v ) return;
   if( type!=TK_DEFERRED ){
     for(i=0; i<db->nDb; i++){
-      sqlite3VdbeAddOp2(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1);
+      sqlite3VdbeAddOp3(v, OP_Transaction, i, (type==TK_EXCLUSIVE)+1, 1);
       sqlite3VdbeUsesBtree(v, i);
     }
   }
   sqlite3VdbeAddOp0(v, OP_AutoCommit);
 }

Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -802,10 +802,11 @@
         u32 mask;    /* Mask of the bit in sqlite3.flags to set/clear */
       } aFlagOp[] = {
         { SQLITE_DBCONFIG_ENABLE_FKEY,           SQLITE_ForeignKeys    },
         { SQLITE_DBCONFIG_ENABLE_TRIGGER,        SQLITE_EnableTrigger  },
         { SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, SQLITE_Fts3Tokenizer  },
+        { SQLITE_DBCONFIG_REQUIRE_TXN,           SQLITE_RequireTxn     },
       };
       unsigned int i;
       rc = SQLITE_ERROR; /* IMP: R-42790-23372 */
       for(i=0; i<ArraySize(aFlagOp); i++){
         if( aFlagOp[i].op==op ){

Index: src/sqlite.h.in
==================================================================
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -1936,10 +1936,11 @@
 */
 #define SQLITE_DBCONFIG_LOOKASIDE             1001 /* void* int int */
 #define SQLITE_DBCONFIG_ENABLE_FKEY           1002 /* int int* */
 #define SQLITE_DBCONFIG_ENABLE_TRIGGER        1003 /* int int* */
 #define SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER 1004 /* int int* */
+#define SQLITE_DBCONFIG_REQUIRE_TXN           1005 /* int int* */
 
 
 /*
 ** CAPI3REF: Enable Or Disable Extended Result Codes
 ** METHOD: sqlite3

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -1382,11 +1382,11 @@
 #define SQLITE_QueryOnly      0x02000000  /* Disable database changes */
 #define SQLITE_VdbeEQP        0x04000000  /* Debug EXPLAIN QUERY PLAN */
 #define SQLITE_Vacuum         0x08000000  /* Currently in a VACUUM */
 #define SQLITE_CellSizeCk     0x10000000  /* Check btree cell sizes on load */
 #define SQLITE_Fts3Tokenizer  0x20000000  /* Enable fts3_tokenizer(2) */
-
+#define SQLITE_RequireTxn     0x40000000  /* BEGIN required to write */
 
 /*
 ** Bits of the sqlite3.dbOptFlags field that are used by the
 ** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface to
 ** selectively disable various optimizations.

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -3084,11 +3084,12 @@
 **
 ** Begin a transaction on database P1 if a transaction is not already
 ** active.
 ** If P2 is non-zero, then a write-transaction is started, or if a 
 ** read-transaction is already active, it is upgraded to a write-transaction.
-** If P2 is zero, then a read-transaction is started.
+** If P2 is zero, then a read-transaction is started.  The 0x02 bit of P2
+** is set for an exclusive transaction.
 **
 ** P1 is the index of the database file on which the transaction is
 ** started.  Index 0 is the main database file and index 1 is the
 ** file used for temporary tables.  Indices of 2 or more are used for
 ** attached databases.
@@ -3101,20 +3102,23 @@
 ** active statements. A statement transaction allows the changes made by this
 ** VDBE to be rolled back after an error without having to roll back the
 ** entire transaction. If no error is encountered, the statement transaction
 ** will automatically commit when the VDBE halts.
 **
-** If P5!=0 then this opcode also checks the schema cookie against P3
+** If P5==1 then this opcode also checks the schema cookie against P3
 ** and the schema generation counter against P4.
 ** The cookie changes its value whenever the database schema changes.
 ** This operation is used to detect when that the cookie has changed
 ** and that the current process needs to reread the schema.  If the schema
 ** cookie in P3 differs from the schema cookie in the database header or
 ** if the schema generation counter in P4 differs from the current
 ** generation counter, then an SQLITE_SCHEMA error is raised and execution
 ** halts.  The sqlite3_step() wrapper function might then reprepare the
 ** statement and rerun it from the beginning.
+**
+** If P5==0 and P3==1 this is the transaction started by a BEGIN 
+** IMMEDIATE or BEGIN EXCLUSIVE command.
 */
 case OP_Transaction: {
   Btree *pBt;
   int iMeta;
   int iGen;
@@ -3121,13 +3125,23 @@
 
   assert( p->bIsReader );
   assert( p->readOnly==0 || pOp->p2==0 );
   assert( pOp->p1>=0 && pOp->p1<db->nDb );
   assert( DbMaskTest(p->btreeMask, pOp->p1) );
-  if( pOp->p2 && (db->flags & SQLITE_QueryOnly)!=0 ){
-    rc = SQLITE_READONLY;
-    goto abort_due_to_error;
+  if( pOp->p2 ){
+    if( (db->flags & SQLITE_QueryOnly)!=0 ){
+      rc = SQLITE_READONLY;
+      goto abort_due_to_error;
+    }
+    if( (db->flags & SQLITE_RequireTxn)!=0 
+     && db->autoCommit
+     && (pOp->p5!=0 || pOp->p3!=1)
+    ){
+      sqlite3VdbeError(p, "cannot write outside of a transaction");
+      rc = SQLITE_ERROR;
+      goto abort_due_to_error;
+    }
   }
   pBt = db->aDb[pOp->p1].pBt;
 
   if( pBt ){
     rc = sqlite3BtreeBeginTrans(pBt, pOp->p2);
@@ -3174,13 +3188,12 @@
     iGen = db->aDb[pOp->p1].pSchema->iGeneration;
   }else{
     iGen = iMeta = 0;
   }
   assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
-  if( pOp->p5 && (iMeta!=pOp->p3 || iGen!=pOp->p4.i) ){
-    sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
+  if( pOp->p5==1 && (iMeta!=pOp->p3 || iGen!=pOp->p4.i) ){
+    sqlite3VdbeError(p, "database schema has changed");
     /* If the schema-cookie from the database file matches the cookie 
     ** stored with the in-memory representation of the schema, do
     ** not reload the schema from the database file.
     **
     ** If virtual-tables are in use, this is not just an optimization.