diff --git a/buildheader/Makefile b/buildheader/Makefile
index 33da9879d20..9022730cc03 100644
--- a/buildheader/Makefile
+++ b/buildheader/Makefile
@@ -12,7 +12,7 @@
 # 4. make hs
 
 BDB = 4_4
-BDBDIR = ../../berkeleydb
+BDBDIR = ../../../berkeleydb
 MYSQL_H = -I$(BDBDIR)/db-4.1.25/build_unix/
 OPTFLAGS = -O2
 CFLAGS = -Wall -W -Werror -g $(OPTFLAGS)
diff --git a/buildheader/db.h_4_4 b/buildheader/db.h_4_4
index 83e93d1ec0b..a137769b835 100644
--- a/buildheader/db.h_4_4
+++ b/buildheader/db.h_4_4
@@ -69,6 +69,7 @@ typedef enum {
 #define DB_INIT_TXN 262144
 #define DB_USE_ENVIRON 2048
 #define DB_USE_ENVIRON_ROOT 4096
+#define DB_READ_UNCOMMITTED 67108864
 #define DB_KEYEMPTY -30997
 #define DB_KEYEXIST -30996
 #define DB_LOCK_DEADLOCK -30995
diff --git a/buildheader/db.h_4_5 b/buildheader/db.h_4_5
index 07dfc891f1e..e327cd4b250 100644
--- a/buildheader/db.h_4_5
+++ b/buildheader/db.h_4_5
@@ -69,6 +69,7 @@ typedef enum {
 #define DB_INIT_TXN 524288
 #define DB_USE_ENVIRON 4096
 #define DB_USE_ENVIRON_ROOT 8192
+#define DB_READ_UNCOMMITTED 134217728
 #define DB_KEYEMPTY -30997
 #define DB_KEYEXIST -30996
 #define DB_LOCK_DEADLOCK -30995
diff --git a/buildheader/db.h_4_6 b/buildheader/db.h_4_6
index a249e2ed5b2..6219ff58533 100644
--- a/buildheader/db.h_4_6
+++ b/buildheader/db.h_4_6
@@ -69,6 +69,7 @@ typedef enum {
 #define DB_INIT_TXN 2097152
 #define DB_USE_ENVIRON 16384
 #define DB_USE_ENVIRON_ROOT 32768
+#define DB_READ_UNCOMMITTED 134217728
 #define DB_KEYEMPTY -30997
 #define DB_KEYEXIST -30996
 #define DB_LOCK_DEADLOCK -30995
diff --git a/buildheader/make_db_h.c b/buildheader/make_db_h.c
index 6d0075e1c72..bfb5469960f 100644
--- a/buildheader/make_db_h.c
+++ b/buildheader/make_db_h.c
@@ -81,6 +81,9 @@ void print_defines (void) {
     dodefine(DB_USE_ENVIRON);
     dodefine(DB_USE_ENVIRON_ROOT);
 
+#ifdef DB_READ_UNCOMMITTED
+    dodefine(DB_READ_UNCOMMITTED);
+#endif
     dodefine(DB_KEYEMPTY);
     dodefine(DB_KEYEXIST);
     dodefine(DB_LOCK_DEADLOCK);
diff --git a/include/db.h b/include/db.h
index 83e93d1ec0b..a137769b835 100644
--- a/include/db.h
+++ b/include/db.h
@@ -69,6 +69,7 @@ typedef enum {
 #define DB_INIT_TXN 262144
 #define DB_USE_ENVIRON 2048
 #define DB_USE_ENVIRON_ROOT 4096
+#define DB_READ_UNCOMMITTED 67108864
 #define DB_KEYEMPTY -30997
 #define DB_KEYEXIST -30996
 #define DB_LOCK_DEADLOCK -30995
diff --git a/src/tests/test_db_txn_locks_read_uncommitted.c b/src/tests/test_db_txn_locks_read_uncommitted.c
new file mode 100644
index 00000000000..a5ce2db345a
--- /dev/null
+++ b/src/tests/test_db_txn_locks_read_uncommitted.c
@@ -0,0 +1,223 @@
+/* -*- mode: C; c-basic-offset: 4 -*- */
+#ident "Copyright (c) 2007 Tokutek Inc.  All rights reserved."
+
+#include <string.h>
+#include <db.h>
+#include <assert.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+#include "test.h"
+
+// ENVDIR is defined in the Makefile
+
+static DB *db;
+static DB_TXN* txns[(int)256];
+static DB_ENV* dbenv;
+static DBC*    cursors[(int)256];
+
+static void
+put(BOOL success, char txn, int _key, int _data) {
+    assert(txns[(int)txn]);
+
+    int r;
+    DBT key;
+    DBT data;
+    
+    r = db->put(db, txns[(int)txn],
+                    dbt_init(&key, &_key, sizeof(int)),
+                    dbt_init(&data, &_data, sizeof(int)),
+                    DB_YESOVERWRITE);
+
+    if (success)    CKERR(r);
+    else            CKERR2s(r, DB_LOCK_DEADLOCK, DB_LOCK_NOTGRANTED);
+}
+
+static void
+init_txn (char name, u_int32_t flags) {
+    int r;
+    assert(!txns[(int)name]);
+    r = dbenv->txn_begin(dbenv, NULL, &txns[(int)name], DB_TXN_NOWAIT | flags);
+        CKERR(r);
+    assert(txns[(int)name]);
+}
+
+static void
+init_dbc (char name) {
+    int r;
+
+    assert(!cursors[(int)name] && txns[(int)name]);
+    r = db->cursor(db, txns[(int)name], &cursors[(int)name], 0);
+        CKERR(r);
+    assert(cursors[(int)name]);
+}
+
+static void
+commit_txn (char name) {
+    int r;
+    assert(txns[(int)name] && !cursors[(int)name]);
+
+    r = txns[(int)name]->commit(txns[(int)name], 0);
+        CKERR(r);
+    txns[(int)name] = NULL;
+}
+
+
+static void
+close_dbc (char name) {
+    int r;
+
+    assert(cursors[(int)name]);
+    r = cursors[(int)name]->c_close(cursors[(int)name]);
+        CKERR(r);
+    cursors[(int)name] = NULL;
+}
+
+static void
+early_commit (char name) {
+    assert(cursors[(int)name] && txns[(int)name]);
+    close_dbc(name);
+    commit_txn(name);
+}
+
+static void
+setup_dbs (u_int32_t dup_flags) {
+    int r;
+
+    system("rm -rf " ENVDIR);
+    mkdir(ENVDIR, 0777);
+    dbenv   = NULL;
+    db      = NULL;
+    /* Open/create primary */
+    r = db_env_create(&dbenv, 0);
+        CKERR(r);
+    u_int32_t env_txn_flags  = DB_INIT_TXN | DB_INIT_LOCK;
+    u_int32_t env_open_flags = DB_CREATE | DB_PRIVATE | DB_INIT_MPOOL;
+	r = dbenv->open(dbenv, ENVDIR, env_open_flags | env_txn_flags, 0600);
+        CKERR(r);
+    
+    r = db_create(&db, dbenv, 0);
+        CKERR(r);
+    if (dup_flags) {
+        r = db->set_flags(db, dup_flags);
+            CKERR(r);
+    }
+    r = db->set_bt_compare( db, int_dbt_cmp);
+    CKERR(r);
+    r = db->set_dup_compare(db, int_dbt_cmp);
+    CKERR(r);
+
+    char a;
+    for (a = 'a'; a <= 'z'; a++) init_txn(a, 0);
+    for (a = '0'; a <= '9'; a++) init_txn(a, DB_READ_UNCOMMITTED);
+    init_txn('\0', 0);
+    r = db->open(db, txns[(int)'\0'], "foobar.db", NULL, DB_BTREE, DB_CREATE | DB_READ_UNCOMMITTED, 0600);
+        CKERR(r);
+    commit_txn('\0');
+    for (a = 'a'; a <= 'z'; a++) init_dbc(a);
+    for (a = '0'; a <= '9'; a++) init_dbc(a);
+}
+
+static void
+close_dbs(void) {
+    char a;
+    for (a = 'a'; a <= 'z'; a++) {
+        if (cursors[(int)a]) close_dbc(a);
+        if (txns[(int)a])    commit_txn(a);
+    }
+    for (a = '0'; a <= '9'; a++) {
+        if (cursors[(int)a]) close_dbc(a);
+        if (txns[(int)a])    commit_txn(a);
+    }
+
+    int r;
+    r = db->close(db, 0);
+        CKERR(r);
+    db      = NULL;
+    r = dbenv->close(dbenv, 0);
+        CKERR(r);
+    dbenv   = NULL;
+}
+
+
+static void
+table_scan(char txn, BOOL success) {
+    int r;
+    DBT key;
+    DBT data;
+
+    assert(txns[(int)txn] && cursors[(int)txn]);
+    r = cursors[(int)txn]->c_get(cursors[(int)txn],
+                                 dbt_init(&key,  0, 0),
+                                 dbt_init(&data, 0, 0),
+                                 DB_FIRST);
+    while (r==0) {
+        r = cursors[(int)txn]->c_get(cursors[(int)txn],
+                                     dbt_init(&key,  0, 0),
+                                     dbt_init(&data, 0, 0),
+                                     DB_NEXT);
+    }
+    if (success) CKERR2(r, DB_NOTFOUND);
+    else         CKERR2s(r, DB_LOCK_NOTGRANTED, DB_LOCK_DEADLOCK);
+}
+
+static void
+table_prelock(char txn, BOOL success) {
+    int r;
+#if defined USE_TDB && USE_TDB
+    r = db->pre_acquire_table_lock(db,  txns[(int)txn]);
+#else
+    DBT key;
+    DBT data;
+
+    assert(txns[(int)txn] && cursors[(int)txn]);
+    r = cursors[(int)txn]->c_get(cursors[(int)txn],
+                                 dbt_init(&key,  0, 0),
+                                 dbt_init(&data, 0, 0),
+                                 DB_FIRST | DB_RMW);
+    while (r==0) {
+        r = cursors[(int)txn]->c_get(cursors[(int)txn],
+                                     dbt_init(&key,  0, 0),
+                                     dbt_init(&data, 0, 0),
+                                     DB_NEXT | DB_RMW);
+    }
+#endif
+    if (success) CKERR(r);
+    else         CKERR2s(r, DB_LOCK_NOTGRANTED, DB_LOCK_DEADLOCK);
+}
+
+static void
+test (u_int32_t dup_flags) {
+    char txn;
+    /* ********************************************************************** */
+    setup_dbs(dup_flags);
+    close_dbs();
+    /* ********************************************************************** */
+    setup_dbs(dup_flags);
+    table_scan('0', TRUE);
+    table_prelock('a', TRUE);
+    put(TRUE, 'a', 0, 0);
+    for (txn = 'b'; txn<'z'; txn++) {
+        table_scan(txn, FALSE);
+    }
+    for (txn = '0'; txn<'9'; txn++) {
+        table_scan(txn, TRUE);
+    }
+    early_commit('a');
+    for (txn = 'b'; txn<'z'; txn++) {
+        table_scan(txn, TRUE);
+    }
+    for (txn = '0'; txn<'9'; txn++) {
+        table_scan(txn, TRUE);
+    }
+    close_dbs();
+    /* ********************************************************************** */
+}
+
+
+int main(int argc, const char* argv[]) {
+    parse_args(argc, argv);
+    test(0);
+    test(DB_DUP | DB_DUPSORT);
+    return 0;
+}
diff --git a/src/ydb-internal.h b/src/ydb-internal.h
index 4a99b9ddbde..87c6b4db3e0 100644
--- a/src/ydb-internal.h
+++ b/src/ydb-internal.h
@@ -73,6 +73,7 @@ struct __toku_db_txn_internal {
     //TXNID txnid64; /* A sixty-four bit txn id. */
     TOKUTXN tokutxn;
     toku_lth* lth;
+    u_int32_t flags;
     DB_TXN *child, *next, *prev;
 };
 
diff --git a/src/ydb.c b/src/ydb.c
index a666ccde735..68b65b5e8b5 100644
--- a/src/ydb.c
+++ b/src/ydb.c
@@ -979,7 +979,7 @@ static int toku_txn_commit(DB_TXN * txn, u_int32_t flags) {
         }
     }
     //toku_ydb_notef("flags=%d\n", flags);
-    int nosync = (flags & DB_TXN_NOSYNC)!=0;
+    int nosync = (flags & DB_TXN_NOSYNC)!=0 || (txn->i->flags&DB_TXN_NOSYNC);
     flags &= ~DB_TXN_NOSYNC;
 
     int r2 = toku_txn_release_locks(txn);
@@ -1056,7 +1056,22 @@ static int toku_txn_begin(DB_ENV *env, DB_TXN * stxn, DB_TXN ** txn, u_int32_t f
     HANDLE_PANICKED_ENV(env);
     if (!toku_logger_is_open(env->i->logger)) return toku_ydb_do_error(env, EINVAL, "Environment does not have logging enabled\n");
     if (!(env->i->open_flags & DB_INIT_TXN))  return toku_ydb_do_error(env, EINVAL, "Environment does not have transactions enabled\n");
-    flags=flags;
+    u_int32_t txn_flags = 0;
+    txn_flags |= DB_TXN_NOWAIT; //We do not support blocking locks.
+    if (flags&DB_READ_UNCOMMITTED) {
+        txn_flags |=  DB_READ_UNCOMMITTED;
+        flags     &= ~DB_READ_UNCOMMITTED;
+    }
+    if (flags&DB_TXN_NOWAIT) {
+        txn_flags |=  DB_TXN_NOWAIT;
+        flags     &= ~DB_TXN_NOWAIT;
+    }
+    if (flags&DB_TXN_NOSYNC) {
+        txn_flags |=  DB_TXN_NOSYNC;
+        flags     &= ~DB_TXN_NOSYNC;
+    }
+    if (flags!=0) return toku_ydb_do_error(env, EINVAL, "Invalid flags passed to DB_ENV->txn_begin\n");
+
     DB_TXN *MALLOC(result);
     if (result == 0)
         return ENOMEM;
@@ -1073,6 +1088,7 @@ static int toku_txn_begin(DB_ENV *env, DB_TXN * stxn, DB_TXN ** txn, u_int32_t f
         return ENOMEM;
     }
     memset(result->i, 0, sizeof *result->i);
+    result->i->flags = txn_flags;
 
     int r;
     if (env->i->open_flags & DB_INIT_LOCK && !stxn) {
@@ -1321,8 +1337,12 @@ typedef struct {
     BOOL        tmp_dat_malloced;
 } C_GET_VARS;
 
-static inline u_int32_t get_prelocked_flags(u_int32_t flags) {
-    return flags & (DB_PRELOCKED | DB_PRELOCKED_WRITE);
+static inline u_int32_t get_prelocked_flags(u_int32_t flags, DB_TXN* txn) {
+    u_int32_t lock_flags = flags & (DB_PRELOCKED | DB_PRELOCKED_WRITE);
+
+    //DB_READ_UNCOMMITTED transactions 'own' all read locks.
+    if (txn && txn->i->flags&DB_READ_UNCOMMITTED) lock_flags |= DB_PRELOCKED;
+    return lock_flags;
 }
 
 static void toku_c_get_fix_flags(C_GET_VARS* g) {
@@ -1351,7 +1371,7 @@ static void toku_c_get_fix_flags(C_GET_VARS* g) {
         default:
             break;
     }
-    g->lock_flags = get_prelocked_flags(g->flag);
+    g->lock_flags = get_prelocked_flags(g->flag, g->c->i->txn);
     g->flag &= ~g->lock_flags;
 }
 
@@ -1690,7 +1710,7 @@ static int toku_c_del_noassociate(DBC * c, u_int32_t flags) {
     HANDLE_PANICKED_DB(db);
     if (toku_c_uninitialized(c)) return EINVAL;
 
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, c->i->txn);
     flags &= ~lock_flags;
 
     int r;
@@ -1843,7 +1863,7 @@ static int locked_c_getf_next_dup(DBC *c, u_int32_t flag, void(*f)(DBT const *ke
 
 static int toku_c_getf_first(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT const *data, void *extra), void *extra) {
     HANDLE_PANICKED_DB(c->dbp);
-    u_int32_t lock_flags = get_prelocked_flags(flag);
+    u_int32_t lock_flags = get_prelocked_flags(flag, c->i->txn);
     flag &= ~lock_flags;
     assert(flag==0);
     TOKUTXN txn = c->i->txn ? c->i->txn->i->tokutxn : NULL;
@@ -1878,7 +1898,7 @@ cleanup:
 
 static int toku_c_getf_last(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT const *data, void *extra), void *extra) {
     HANDLE_PANICKED_DB(c->dbp);
-    u_int32_t lock_flags = get_prelocked_flags(flag);
+    u_int32_t lock_flags = get_prelocked_flags(flag, c->i->txn);
     flag &= ~lock_flags;
     assert(flag==0);
     TOKUTXN txn = c->i->txn ? c->i->txn->i->tokutxn : NULL;
@@ -1914,7 +1934,7 @@ cleanup:
 static int toku_c_getf_next(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT const *data, void *extra), void *extra) {
     HANDLE_PANICKED_DB(c->dbp);
     if (toku_c_uninitialized(c)) return toku_c_getf_first(c, flag, f, extra);
-    u_int32_t lock_flags = get_prelocked_flags(flag);
+    u_int32_t lock_flags = get_prelocked_flags(flag, c->i->txn);
     flag &= ~lock_flags;
     assert(flag==0);
     TOKUTXN txn = c->i->txn ? c->i->txn->i->tokutxn : NULL;
@@ -1959,7 +1979,7 @@ static int toku_c_getf_next(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT
 static int toku_c_getf_prev(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT const *data, void *extra), void *extra) {
     HANDLE_PANICKED_DB(c->dbp);
     if (toku_c_uninitialized(c)) return toku_c_getf_last(c, flag, f, extra);
-    u_int32_t lock_flags = get_prelocked_flags(flag);
+    u_int32_t lock_flags = get_prelocked_flags(flag, c->i->txn);
     flag &= ~lock_flags;
     assert(flag==0);
     TOKUTXN txn = c->i->txn ? c->i->txn->i->tokutxn : NULL;
@@ -2004,7 +2024,7 @@ static int toku_c_getf_prev(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT
 static int toku_c_getf_next_dup(DBC *c, u_int32_t flag, void(*f)(DBT const *key, DBT const *data, void *extra), void *extra) {
     HANDLE_PANICKED_DB(c->dbp);
     if (toku_c_uninitialized(c)) return EINVAL;
-    u_int32_t lock_flags = get_prelocked_flags(flag);
+    u_int32_t lock_flags = get_prelocked_flags(flag, c->i->txn);
     flag &= ~lock_flags;
     assert(flag==0);
     TOKUTXN txn = c->i->txn ? c->i->txn->i->tokutxn : NULL;
@@ -2057,7 +2077,7 @@ static int toku_c_getf_heavi(DBC *c, u_int32_t flags,
     if (direction==0) return EINVAL;
     DBC *tmp_c = NULL;
     int r;
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, c->i->txn);
     flags &= ~lock_flags;
     assert(flags==0);
     struct heavi_wrapper wrapper;
@@ -2221,7 +2241,7 @@ finish:
 
 static int toku_db_get_noassociate(DB * db, DB_TXN * txn, DBT * key, DBT * data, u_int32_t flags) {
     int r;
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, txn);
     flags &= ~lock_flags;
     if (flags!=0 && flags!=DB_GET_BOTH) return EINVAL;
 
@@ -2236,7 +2256,7 @@ static int toku_db_get_noassociate(DB * db, DB_TXN * txn, DBT * key, DBT * data,
 
 static int toku_db_del_noassociate(DB * db, DB_TXN * txn, DBT * key, u_int32_t flags) {
     int r;
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, txn);
     flags &= ~lock_flags;
     if (flags!=0 && flags!=DB_DELETE_ANY) return EINVAL;
     //DB_DELETE_ANY supresses the BDB DB->del return value indicating that the key was not found prior to the delete
@@ -2592,7 +2612,7 @@ static int toku_db_delboth_noassociate(DB *db, DB_TXN *txn, DBT *key, DBT *val,
     HANDLE_PANICKED_DB(db);
     int r;
 
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, txn);
     flags &= ~lock_flags;
     u_int32_t delete_any = flags&DB_DELETE_ANY;
     flags &= ~DB_DELETE_ANY;
@@ -2645,7 +2665,7 @@ static int toku_db_get (DB * db, DB_TXN * txn, DBT * key, DBT * data, u_int32_t
     if ((db->i->open_flags & DB_THREAD) && db_thread_need_flags(data))
         return EINVAL;
 
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, txn);
     flags &= ~lock_flags;
     if (flags != 0 && flags != DB_GET_BOTH) return EINVAL;
     // We aren't ready to handle flags such as DB_READ_COMMITTED or DB_READ_UNCOMMITTED or DB_RMW
@@ -2811,6 +2831,8 @@ static int toku_db_open(DB * db, DB_TXN * txn, const char *fname, const char *db
     int is_db_excl    = flags & DB_EXCL;    flags&=~DB_EXCL;
     int is_db_create  = flags & DB_CREATE;  flags&=~DB_CREATE;
     int is_db_rdonly  = flags & DB_RDONLY;  flags&=~DB_RDONLY;
+    //We support READ_UNCOMMITTED whether or not the flag is provided.
+                                            flags&=~DB_READ_UNCOMMITTED;
     if (dbtype != DB_UNKNOWN && dbtype != DB_BTREE) return EINVAL;
     if (flags & ~DB_THREAD) return EINVAL; // unknown flags
 
@@ -2935,7 +2957,7 @@ static int toku_db_put_noassociate(DB * db, DB_TXN * txn, DBT * key, DBT * data,
         if (key->size >= limit || data->size >= limit)
             return toku_ydb_do_error(db->dbenv, EINVAL, "The largest key or data item allowed is %d bytes", limit);
     }
-    u_int32_t lock_flags = get_prelocked_flags(flags);
+    u_int32_t lock_flags = get_prelocked_flags(flags, txn);
     flags &= ~lock_flags;
 
     if (flags == DB_YESOVERWRITE) {
@@ -3191,6 +3213,8 @@ cleanup:
 int toku_db_pre_acquire_read_lock(DB *db, DB_TXN *txn, const DBT *key_left, const DBT *val_left, const DBT *key_right, const DBT *val_right) {
     HANDLE_PANICKED_DB(db);
     if (!db->i->lt || !txn) return EINVAL;
+    //READ_UNCOMMITTED transactions do not need read locks.
+    if (txn->i->flags&DB_READ_UNCOMMITTED) return 0;
 
     DB_TXN* txn_anc = toku_txn_ancestor(txn);
     int r;