diff --git a/ledis/const.go b/ledis/const.go
index 5d4b587..9bb0b70 100644
--- a/ledis/const.go
+++ b/ledis/const.go
@@ -6,6 +6,43 @@ import (
 
 const Version = "0.4"
 
+type DataType byte
+
+// for out use
+const (
+	KV DataType = iota
+	LIST
+	HASH
+	SET
+	ZSET
+)
+
+func (d DataType) String() string {
+	switch d {
+	case KV:
+		return KVName
+	case LIST:
+		return ListName
+	case HASH:
+		return HashName
+	case SET:
+		return SetName
+	case ZSET:
+		return ZSetName
+	default:
+		return "unknown"
+	}
+}
+
+const (
+	KVName   = "KV"
+	ListName = "LIST"
+	HashName = "HASH"
+	SetName  = "SET"
+	ZSetName = "ZSET"
+)
+
+// for backend store
 const (
 	NoneType    byte = 0
 	KVType      byte = 1
diff --git a/ledis/ledis_db.go b/ledis/ledis_db.go
index ebde98e..4e2b490 100644
--- a/ledis/ledis_db.go
+++ b/ledis/ledis_db.go
@@ -128,7 +128,7 @@ func (db *DB) flushType(t *batch, dataType byte) (drop int64, err error) {
 	}
 
 	var keys [][]byte
-	keys, err = db.scan(metaDataType, nil, 1024, false, "")
+	keys, err = db.scanGeneric(metaDataType, nil, 1024, false, "", false)
 	for len(keys) != 0 || err != nil {
 		for _, key := range keys {
 			deleteFunc(t, key)
@@ -141,7 +141,7 @@ func (db *DB) flushType(t *batch, dataType byte) (drop int64, err error) {
 		} else {
 			drop += int64(len(keys))
 		}
-		keys, err = db.scan(metaDataType, nil, 1024, false, "")
+		keys, err = db.scanGeneric(metaDataType, nil, 1024, false, "", false)
 	}
 	return
 }
diff --git a/ledis/scan.go b/ledis/scan.go
index 9e8e235..5b32133 100644
--- a/ledis/scan.go
+++ b/ledis/scan.go
@@ -9,15 +9,46 @@ import (
 var errDataType = errors.New("error data type")
 var errMetaKey = errors.New("error meta key")
 
-func (db *DB) scan(dataType byte, key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scanGeneric(dataType, key, count, inclusive, match, false)
+//fif inclusive is true, scan range [cursor, inf) else (cursor, inf)
+func (db *DB) Scan(dataType DataType, cursor []byte, count int, inclusive bool, match string) ([][]byte, error) {
+	storeDataType, err := getDataStoreType(dataType)
+	if err != nil {
+		return nil, err
+	}
+
+	return db.scanGeneric(storeDataType, cursor, count, inclusive, match, false)
 }
 
-func (db *DB) revscan(dataType byte, key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scanGeneric(dataType, key, count, inclusive, match, true)
+//if inclusive is true, revscan range (-inf, cursor] else (inf, cursor)
+func (db *DB) RevScan(dataType DataType, cursor []byte, count int, inclusive bool, match string) ([][]byte, error) {
+	storeDataType, err := getDataStoreType(dataType)
+	if err != nil {
+		return nil, err
+	}
+
+	return db.scanGeneric(storeDataType, cursor, count, inclusive, match, true)
 }
 
-func (db *DB) scanGeneric(dataType byte, key []byte, count int,
+func getDataStoreType(dataType DataType) (byte, error) {
+	var storeDataType byte
+	switch dataType {
+	case KV:
+		storeDataType = KVType
+	case LIST:
+		storeDataType = LMetaType
+	case HASH:
+		storeDataType = HSizeType
+	case SET:
+		storeDataType = SSizeType
+	case ZSET:
+		storeDataType = ZSizeType
+	default:
+		return 0, errDataType
+	}
+	return storeDataType, nil
+}
+
+func (db *DB) scanGeneric(storeDataType byte, key []byte, count int,
 	inclusive bool, match string, reverse bool) ([][]byte, error) {
 	var minKey, maxKey []byte
 	var err error
@@ -32,10 +63,10 @@ func (db *DB) scanGeneric(dataType byte, key []byte, count int,
 	tp := store.RangeOpen
 
 	if !reverse {
-		if minKey, err = db.encodeScanMinKey(dataType, key); err != nil {
+		if minKey, err = db.encodeScanMinKey(storeDataType, key); err != nil {
 			return nil, err
 		}
-		if maxKey, err = db.encodeScanMaxKey(dataType, nil); err != nil {
+		if maxKey, err = db.encodeScanMaxKey(storeDataType, nil); err != nil {
 			return nil, err
 		}
 
@@ -43,10 +74,10 @@ func (db *DB) scanGeneric(dataType byte, key []byte, count int,
 			tp = store.RangeROpen
 		}
 	} else {
-		if minKey, err = db.encodeScanMinKey(dataType, nil); err != nil {
+		if minKey, err = db.encodeScanMinKey(storeDataType, nil); err != nil {
 			return nil, err
 		}
-		if maxKey, err = db.encodeScanMaxKey(dataType, key); err != nil {
+		if maxKey, err = db.encodeScanMaxKey(storeDataType, key); err != nil {
 			return nil, err
 		}
 
@@ -69,7 +100,7 @@ func (db *DB) scanGeneric(dataType byte, key []byte, count int,
 	v := make([][]byte, 0, count)
 
 	for i := 0; it.Valid() && i < count; it.Next() {
-		if k, err := db.decodeScanKey(dataType, it.Key()); err != nil {
+		if k, err := db.decodeScanKey(storeDataType, it.Key()); err != nil {
 			continue
 		} else if r != nil && !r.Match(k) {
 			continue
@@ -82,36 +113,36 @@ func (db *DB) scanGeneric(dataType byte, key []byte, count int,
 	return v, nil
 }
 
-func (db *DB) encodeScanMinKey(dataType byte, key []byte) ([]byte, error) {
+func (db *DB) encodeScanMinKey(storeDataType byte, key []byte) ([]byte, error) {
 	if len(key) == 0 {
-		return db.encodeScanKey(dataType, nil)
+		return db.encodeScanKey(storeDataType, nil)
 	} else {
 		if err := checkKeySize(key); err != nil {
 			return nil, err
 		}
-		return db.encodeScanKey(dataType, key)
+		return db.encodeScanKey(storeDataType, key)
 	}
 }
 
-func (db *DB) encodeScanMaxKey(dataType byte, key []byte) ([]byte, error) {
+func (db *DB) encodeScanMaxKey(storeDataType byte, key []byte) ([]byte, error) {
 	if len(key) > 0 {
 		if err := checkKeySize(key); err != nil {
 			return nil, err
 		}
 
-		return db.encodeScanKey(dataType, key)
+		return db.encodeScanKey(storeDataType, key)
 	}
 
-	k, err := db.encodeScanKey(dataType, nil)
+	k, err := db.encodeScanKey(storeDataType, nil)
 	if err != nil {
 		return nil, err
 	}
-	k[len(k)-1] = dataType + 1
+	k[len(k)-1] = storeDataType + 1
 	return k, nil
 }
 
-func (db *DB) encodeScanKey(dataType byte, key []byte) ([]byte, error) {
-	switch dataType {
+func (db *DB) encodeScanKey(storeDataType byte, key []byte) ([]byte, error) {
+	switch storeDataType {
 	case KVType:
 		return db.encodeKVKey(key), nil
 	case LMetaType:
@@ -128,8 +159,8 @@ func (db *DB) encodeScanKey(dataType byte, key []byte) ([]byte, error) {
 		return nil, errDataType
 	}
 }
-func (db *DB) decodeScanKey(dataType byte, ek []byte) ([]byte, error) {
-	if len(ek) < 2 || ek[0] != db.index || ek[1] != dataType {
+func (db *DB) decodeScanKey(storeDataType byte, ek []byte) ([]byte, error) {
+	if len(ek) < 2 || ek[0] != db.index || ek[1] != storeDataType {
 		return nil, errMetaKey
 	}
 	return ek[2:], nil
diff --git a/ledis/scan_test.go b/ledis/scan_test.go
index b2a0970..ded982c 100644
--- a/ledis/scan_test.go
+++ b/ledis/scan_test.go
@@ -21,13 +21,13 @@ func TestDBScan(t *testing.T) {
 
 	db.FlushAll()
 
-	if v, err := db.Scan(nil, 10, true, ""); err != nil {
+	if v, err := db.Scan(KV, nil, 10, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 0 {
 		t.Fatal(len(v))
 	}
 
-	if v, err := db.RevScan(nil, 10, true, ""); err != nil {
+	if v, err := db.RevScan(KV, nil, 10, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 0 {
 		t.Fatal(len(v))
@@ -37,73 +37,73 @@ func TestDBScan(t *testing.T) {
 	db.Set([]byte("b"), []byte{})
 	db.Set([]byte("c"), []byte{})
 
-	if v, err := db.Scan(nil, 1, true, ""); err != nil {
+	if v, err := db.Scan(KV, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "a")
 	}
 
-	if v, err := db.Scan([]byte("a"), 2, false, ""); err != nil {
+	if v, err := db.Scan(KV, []byte("a"), 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "b", "c")
 	}
 
-	if v, err := db.Scan(nil, 3, true, ""); err != nil {
+	if v, err := db.Scan(KV, nil, 3, true, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "a", "b", "c")
 	}
 
-	if v, err := db.Scan(nil, 3, true, "b"); err != nil {
+	if v, err := db.Scan(KV, nil, 3, true, "b"); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "b")
 	}
 
-	if v, err := db.Scan(nil, 3, true, "."); err != nil {
+	if v, err := db.Scan(KV, nil, 3, true, "."); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "a", "b", "c")
 	}
 
-	if v, err := db.Scan(nil, 3, true, "a+"); err != nil {
+	if v, err := db.Scan(KV, nil, 3, true, "a+"); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "a")
 	}
 
-	if v, err := db.RevScan(nil, 1, true, ""); err != nil {
+	if v, err := db.RevScan(KV, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "c")
 	}
 
-	if v, err := db.RevScan([]byte("c"), 2, false, ""); err != nil {
+	if v, err := db.RevScan(KV, []byte("c"), 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "b", "a")
 	}
 
-	if v, err := db.RevScan(nil, 3, true, ""); err != nil {
+	if v, err := db.RevScan(KV, nil, 3, true, ""); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "c", "b", "a")
 	}
 
-	if v, err := db.RevScan(nil, 3, true, "b"); err != nil {
+	if v, err := db.RevScan(KV, nil, 3, true, "b"); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "b")
 	}
 
-	if v, err := db.RevScan(nil, 3, true, "."); err != nil {
+	if v, err := db.RevScan(KV, nil, 3, true, "."); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "c", "b", "a")
 	}
 
-	if v, err := db.RevScan(nil, 3, true, "c+"); err != nil {
+	if v, err := db.RevScan(KV, nil, 3, true, "c+"); err != nil {
 		t.Fatal(err)
 	} else {
 		checkTestScan(t, v, "c")
@@ -125,7 +125,7 @@ func TestDBHScan(t *testing.T) {
 	k3 := []byte("k3")
 	db.HSet(k3, []byte("3"), []byte{})
 
-	if v, err := db.HScan(nil, 1, true, ""); err != nil {
+	if v, err := db.Scan(HASH, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 1 {
 		t.Fatal("invalid length ", len(v))
@@ -133,7 +133,7 @@ func TestDBHScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[0]))
 	}
 
-	if v, err := db.HScan(k1, 2, true, ""); err != nil {
+	if v, err := db.Scan(HASH, k1, 2, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -143,7 +143,7 @@ func TestDBHScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[1]))
 	}
 
-	if v, err := db.HScan(k1, 2, false, ""); err != nil {
+	if v, err := db.Scan(HASH, k1, 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -169,7 +169,7 @@ func TestDBZScan(t *testing.T) {
 	k3 := []byte("k3")
 	db.ZAdd(k3, ScorePair{3, []byte("m")})
 
-	if v, err := db.ZScan(nil, 1, true, ""); err != nil {
+	if v, err := db.Scan(ZSET, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 1 {
 		t.Fatal("invalid length ", len(v))
@@ -177,7 +177,7 @@ func TestDBZScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[0]))
 	}
 
-	if v, err := db.ZScan(k1, 2, true, ""); err != nil {
+	if v, err := db.Scan(ZSET, k1, 2, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -187,7 +187,7 @@ func TestDBZScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[1]))
 	}
 
-	if v, err := db.ZScan(k1, 2, false, ""); err != nil {
+	if v, err := db.Scan(ZSET, k1, 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -219,7 +219,7 @@ func TestDBLScan(t *testing.T) {
 		t.Fatal(err.Error())
 	}
 
-	if v, err := db.LScan(nil, 1, true, ""); err != nil {
+	if v, err := db.Scan(LIST, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 1 {
 		t.Fatal("invalid length ", len(v))
@@ -227,7 +227,7 @@ func TestDBLScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[0]))
 	}
 
-	if v, err := db.LScan(k1, 2, true, ""); err != nil {
+	if v, err := db.Scan(LIST, k1, 2, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -237,7 +237,7 @@ func TestDBLScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[1]))
 	}
 
-	if v, err := db.LScan(k1, 2, false, ""); err != nil {
+	if v, err := db.Scan(LIST, k1, 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -249,56 +249,6 @@ func TestDBLScan(t *testing.T) {
 
 }
 
-func TestDBBScan(t *testing.T) {
-	// db := getTestDB()
-
-	// db.bFlush()
-
-	// k1 := []byte("k1")
-	// if _, err := db.BSetBit(k1, 1, 1); err != nil {
-	// 	t.Fatal(err.Error())
-	// }
-
-	// k2 := []byte("k2")
-	// if _, err := db.BSetBit(k2, 1, 1); err != nil {
-	// 	t.Fatal(err.Error())
-	// }
-	// k3 := []byte("k3")
-
-	// if _, err := db.BSetBit(k3, 1, 0); err != nil {
-	// 	t.Fatal(err.Error())
-	// }
-
-	// if v, err := db.BScan(nil, 1, true, ""); err != nil {
-	// 	t.Fatal(err)
-	// } else if len(v) != 1 {
-	// 	t.Fatal("invalid length ", len(v))
-	// } else if string(v[0]) != "k1" {
-	// 	t.Fatal("invalid value ", string(v[0]))
-	// }
-
-	// if v, err := db.BScan(k1, 2, true, ""); err != nil {
-	// 	t.Fatal(err)
-	// } else if len(v) != 2 {
-	// 	t.Fatal("invalid length ", len(v))
-	// } else if string(v[0]) != "k1" {
-	// 	t.Fatal("invalid value ", string(v[0]))
-	// } else if string(v[1]) != "k2" {
-	// 	t.Fatal("invalid value ", string(v[1]))
-	// }
-
-	// if v, err := db.BScan(k1, 2, false, ""); err != nil {
-	// 	t.Fatal(err)
-	// } else if len(v) != 2 {
-	// 	t.Fatal("invalid length ", len(v))
-	// } else if string(v[0]) != "k2" {
-	// 	t.Fatal("invalid value ", string(v[0]))
-	// } else if string(v[1]) != "k3" {
-	// 	t.Fatal("invalid value ", string(v[1]))
-	// }
-
-}
-
 func TestDBSScan(t *testing.T) {
 	db := getTestDB()
 
@@ -319,7 +269,7 @@ func TestDBSScan(t *testing.T) {
 		t.Fatal(err.Error())
 	}
 
-	if v, err := db.SScan(nil, 1, true, ""); err != nil {
+	if v, err := db.Scan(SET, nil, 1, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 1 {
 		t.Fatal("invalid length ", len(v))
@@ -327,7 +277,7 @@ func TestDBSScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[0]))
 	}
 
-	if v, err := db.SScan(k1, 2, true, ""); err != nil {
+	if v, err := db.Scan(SET, k1, 2, true, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
@@ -337,7 +287,7 @@ func TestDBSScan(t *testing.T) {
 		t.Fatal("invalid value ", string(v[1]))
 	}
 
-	if v, err := db.SScan(k1, 2, false, ""); err != nil {
+	if v, err := db.Scan(SET, k1, 2, false, ""); err != nil {
 		t.Fatal(err)
 	} else if len(v) != 2 {
 		t.Fatal("invalid length ", len(v))
diff --git a/ledis/t_bit.go b/ledis/t_bit.go
index cff51d6..d89f15b 100644
--- a/ledis/t_bit.go
+++ b/ledis/t_bit.go
@@ -922,16 +922,6 @@ func (db *DB) BPersist(key []byte) (int64, error) {
 	return n, err
 }
 
-func (db *DB) BScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	log.Error("bitmap type will be deprecated later, please use bit operations in kv type")
-	return db.scan(BitMetaType, key, count, inclusive, match)
-}
-
-func (db *DB) BRevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	log.Error("bitmap type will be deprecated later, please use bit operations in kv type")
-	return db.revscan(BitMetaType, key, count, inclusive, match)
-}
-
 func (db *DB) bFlush() (drop int64, err error) {
 	t := db.binBatch
 	t.Lock()
diff --git a/ledis/t_hash.go b/ledis/t_hash.go
index 6235acc..3a0133a 100644
--- a/ledis/t_hash.go
+++ b/ledis/t_hash.go
@@ -460,14 +460,6 @@ func (db *DB) hFlush() (drop int64, err error) {
 	return db.flushType(t, HashType)
 }
 
-func (db *DB) HScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scan(HSizeType, key, count, inclusive, match)
-}
-
-func (db *DB) HRevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.revscan(HSizeType, key, count, inclusive, match)
-}
-
 func (db *DB) HExpire(key []byte, duration int64) (int64, error) {
 	if duration <= 0 {
 		return 0, errExpireValue
diff --git a/ledis/t_hash_test.go b/ledis/t_hash_test.go
index 7fac691..6afa2da 100644
--- a/ledis/t_hash_test.go
+++ b/ledis/t_hash_test.go
@@ -114,7 +114,7 @@ func TestHFlush(t *testing.T) {
 		}
 	}
 
-	if v, err := db.HScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(HASH, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 2000 {
 		t.Fatal("invalid value ", len(v))
@@ -135,7 +135,7 @@ func TestHFlush(t *testing.T) {
 		t.Fatal("invalid value ", n)
 	}
 
-	if v, err := db.HScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(HASH, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 0 {
 		t.Fatal("invalid value length ", len(v))
diff --git a/ledis/t_kv.go b/ledis/t_kv.go
index 398d2a8..eb2f1fe 100644
--- a/ledis/t_kv.go
+++ b/ledis/t_kv.go
@@ -347,16 +347,6 @@ func (db *DB) flush() (drop int64, err error) {
 	return db.flushType(t, KVType)
 }
 
-//if inclusive is true, scan range [key, inf) else (key, inf)
-func (db *DB) Scan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scan(KVType, key, count, inclusive, match)
-}
-
-//if inclusive is true, revscan range (-inf, key] else (inf, key)
-func (db *DB) RevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.revscan(KVType, key, count, inclusive, match)
-}
-
 func (db *DB) Expire(key []byte, duration int64) (int64, error) {
 	if duration <= 0 {
 		return 0, errExpireValue
diff --git a/ledis/t_kv_test.go b/ledis/t_kv_test.go
index 63ea052..ffbac81 100644
--- a/ledis/t_kv_test.go
+++ b/ledis/t_kv_test.go
@@ -282,7 +282,7 @@ func TestKVFlush(t *testing.T) {
 		}
 	}
 
-	if v, err := db.Scan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(KV, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 2000 {
 		t.Fatal("invalid value ", len(v))
@@ -303,7 +303,7 @@ func TestKVFlush(t *testing.T) {
 		t.Fatal("invalid value ", n)
 	}
 
-	if v, err := db.Scan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(KV, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 0 {
 		t.Fatal("invalid value length ", len(v))
diff --git a/ledis/t_list.go b/ledis/t_list.go
index 93c6ba2..c2cc5a9 100644
--- a/ledis/t_list.go
+++ b/ledis/t_list.go
@@ -480,14 +480,6 @@ func (db *DB) LPersist(key []byte) (int64, error) {
 	return n, err
 }
 
-func (db *DB) LScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scan(LMetaType, key, count, inclusive, match)
-}
-
-func (db *DB) LRevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.revscan(LMetaType, key, count, inclusive, match)
-}
-
 func (db *DB) lEncodeMinKey() []byte {
 	return db.lEncodeMetaKey(nil)
 }
diff --git a/ledis/t_list_test.go b/ledis/t_list_test.go
index b80af1d..58c1c58 100644
--- a/ledis/t_list_test.go
+++ b/ledis/t_list_test.go
@@ -145,7 +145,7 @@ func TestLFlush(t *testing.T) {
 		}
 	}
 
-	if v, err := db.LScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(LIST, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 2000 {
 		t.Fatal("invalid value ", len(v))
@@ -157,7 +157,7 @@ func TestLFlush(t *testing.T) {
 		t.Fatal("invalid value ", n)
 	}
 
-	if v, err := db.LScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(LIST, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 0 {
 		t.Fatal("invalid value length ", len(v))
diff --git a/ledis/t_set.go b/ledis/t_set.go
index 126b407..200d66b 100644
--- a/ledis/t_set.go
+++ b/ledis/t_set.go
@@ -607,11 +607,3 @@ func (db *DB) SPersist(key []byte) (int64, error) {
 	err = t.Commit()
 	return n, err
 }
-
-func (db *DB) SScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scan(SSizeType, key, count, inclusive, match)
-}
-
-func (db *DB) SRevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.revscan(SSizeType, key, count, inclusive, match)
-}
diff --git a/ledis/t_set_test.go b/ledis/t_set_test.go
index eb24bdb..b6b1460 100644
--- a/ledis/t_set_test.go
+++ b/ledis/t_set_test.go
@@ -352,7 +352,7 @@ func TestSFlush(t *testing.T) {
 		}
 	}
 
-	if v, err := db.SScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(SET, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 2000 {
 		t.Fatal("invalid value ", len(v))
@@ -364,7 +364,7 @@ func TestSFlush(t *testing.T) {
 		t.Fatal("invalid value ", n)
 	}
 
-	if v, err := db.SScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(SET, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 0 {
 		t.Fatal("invalid value length ", len(v))
diff --git a/ledis/t_zset.go b/ledis/t_zset.go
index 36f886b..0bd22a3 100644
--- a/ledis/t_zset.go
+++ b/ledis/t_zset.go
@@ -936,14 +936,6 @@ func (db *DB) ZInterStore(destKey []byte, srcKeys [][]byte, weights []int64, agg
 	return n, nil
 }
 
-func (db *DB) ZScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.scan(ZSizeType, key, count, inclusive, match)
-}
-
-func (db *DB) ZRevScan(key []byte, count int, inclusive bool, match string) ([][]byte, error) {
-	return db.revscan(ZSizeType, key, count, inclusive, match)
-}
-
 func (db *DB) ZRangeByLex(key []byte, min []byte, max []byte, rangeType uint8, offset int, count int) ([][]byte, error) {
 	if min == nil {
 		min = db.zEncodeStartSetKey(key)
diff --git a/ledis/t_zset_test.go b/ledis/t_zset_test.go
index cdb35bc..6323091 100644
--- a/ledis/t_zset_test.go
+++ b/ledis/t_zset_test.go
@@ -391,7 +391,7 @@ func TestZScan(t *testing.T) {
 		}
 	}
 
-	if v, err := db.ZScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(ZSET, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 2000 {
 		t.Fatal("invalid value ", len(v))
@@ -403,7 +403,7 @@ func TestZScan(t *testing.T) {
 		t.Fatal("invalid value ", n)
 	}
 
-	if v, err := db.ZScan(nil, 3000, true, ""); err != nil {
+	if v, err := db.Scan(ZSET, nil, 3000, true, ""); err != nil {
 		t.Fatal(err.Error())
 	} else if len(v) != 0 {
 		t.Fatal("invalid value length ", len(v))
diff --git a/server/cmd_bit.go b/server/cmd_bit.go
index ac577ea..45d6ede 100644
--- a/server/cmd_bit.go
+++ b/server/cmd_bit.go
@@ -274,14 +274,6 @@ func bpersistCommand(c *client) error {
 	return nil
 }
 
-func bxscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.BScan)
-}
-
-func bxrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.BRevScan)
-}
-
 func init() {
 	register("bget", bgetCommand)
 	register("bdelete", bdeleteCommand)
@@ -294,8 +286,4 @@ func init() {
 	register("bexpireat", bexpireAtCommand)
 	register("bttl", bttlCommand)
 	register("bpersist", bpersistCommand)
-	register("bxscan", bxscanCommand)
-	register("bxrevscan", bxrevscanCommand)
-	register("xbscan", bxscanCommand)
-	register("xbrevscan", bxrevscanCommand)
 }
diff --git a/server/cmd_hash.go b/server/cmd_hash.go
index 8c277ee..b9acc85 100644
--- a/server/cmd_hash.go
+++ b/server/cmd_hash.go
@@ -292,14 +292,6 @@ func hpersistCommand(c *client) error {
 	return nil
 }
 
-func hxscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.HScan)
-}
-
-func hxrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.HRevScan)
-}
-
 func xhexistsCommand(c *client) error {
 	args := c.args
 	if len(args) != 1 {
@@ -334,9 +326,5 @@ func init() {
 	register("hexpireat", hexpireAtCommand)
 	register("httl", httlCommand)
 	register("hpersist", hpersistCommand)
-	register("hxscan", hxscanCommand)
-	register("hxrevscan", hxrevscanCommand)
-	register("xhscan", hxscanCommand)
-	register("xhrevscan", hxrevscanCommand)
 	register("xhexists", xhexistsCommand)
 }
diff --git a/server/cmd_kv.go b/server/cmd_kv.go
index 45a4b7a..25d7bb9 100644
--- a/server/cmd_kv.go
+++ b/server/cmd_kv.go
@@ -1,10 +1,8 @@
 package server
 
 import (
-	"github.com/siddontang/go/hack"
 	"github.com/siddontang/ledisdb/ledis"
 	"strconv"
-	"strings"
 )
 
 // func getCommand(c *client) error {
@@ -315,82 +313,6 @@ func persistCommand(c *client) error {
 	return nil
 }
 
-func parseScanArgs(c *client) (key []byte, match string, count int, err error) {
-	args := c.args
-	count = 10
-
-	switch len(args) {
-	case 0:
-		key = nil
-		return
-	case 1, 3, 5:
-		key = args[0]
-		break
-	default:
-		err = ErrCmdParams
-		return
-	}
-
-	if len(args) == 3 {
-		switch strings.ToLower(hack.String(args[1])) {
-		case "match":
-			match = hack.String(args[2])
-		case "count":
-			count, err = strconv.Atoi(hack.String(args[2]))
-		default:
-			err = ErrCmdParams
-			return
-		}
-	} else if len(args) == 5 {
-		if strings.ToLower(hack.String(args[1])) != "match" {
-			err = ErrCmdParams
-			return
-		} else if strings.ToLower(hack.String(args[3])) != "count" {
-			err = ErrCmdParams
-			return
-		}
-
-		match = hack.String(args[2])
-		count, err = strconv.Atoi(hack.String(args[4]))
-	}
-
-	if count <= 0 {
-		err = ErrCmdParams
-	}
-
-	return
-}
-
-func xscanGeneric(c *client,
-	f func(key []byte, count int, inclusive bool, match string) ([][]byte, error)) error {
-	key, match, count, err := parseScanArgs(c)
-	if err != nil {
-		return err
-	}
-
-	if ay, err := f(key, count, false, match); err != nil {
-		return err
-	} else {
-		data := make([]interface{}, 2)
-		if len(ay) < count {
-			data[0] = []byte("")
-		} else {
-			data[0] = ay[len(ay)-1]
-		}
-		data[1] = ay
-		c.resp.writeArray(data)
-	}
-	return nil
-}
-
-func xscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.Scan)
-}
-
-func xrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.RevScan)
-}
-
 func appendCommand(c *client) error {
 	args := c.args
 	if len(args) != 2 {
@@ -619,6 +541,4 @@ func init() {
 	register("expireat", expireAtCommand)
 	register("ttl", ttlCommand)
 	register("persist", persistCommand)
-	register("xscan", xscanCommand)
-	register("xrevscan", xrevscanCommand)
 }
diff --git a/server/cmd_list.go b/server/cmd_list.go
index 7000a74..d3ac6e2 100644
--- a/server/cmd_list.go
+++ b/server/cmd_list.go
@@ -231,14 +231,6 @@ func lpersistCommand(c *client) error {
 	return nil
 }
 
-func lxscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.LScan)
-}
-
-func lxrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.LRevScan)
-}
-
 func blpopCommand(c *client) error {
 	keys, timeout, err := lParseBPopArgs(c)
 	if err != nil {
@@ -317,9 +309,5 @@ func init() {
 	register("lexpireat", lexpireAtCommand)
 	register("lttl", lttlCommand)
 	register("lpersist", lpersistCommand)
-	register("lxscan", lxscanCommand)
-	register("lxrevscan", lxrevscanCommand)
-	register("xlscan", lxscanCommand)
-	register("xlrevscan", lxrevscanCommand)
 	register("xlexists", xlexistsCommand)
 }
diff --git a/server/cmd_migrate.go b/server/cmd_migrate.go
index 3153821..a162328 100644
--- a/server/cmd_migrate.go
+++ b/server/cmd_migrate.go
@@ -165,15 +165,15 @@ func xttl(db *ledis.DB, tp string, key []byte) (int64, error) {
 func xscan(db *ledis.DB, tp string, count int) ([][]byte, error) {
 	switch strings.ToUpper(tp) {
 	case "KV":
-		return db.Scan(nil, count, false, "")
+		return db.Scan(KV, nil, count, false, "")
 	case "HASH":
-		return db.HScan(nil, count, false, "")
+		return db.Scan(HASH, nil, count, false, "")
 	case "LIST":
-		return db.LScan(nil, count, false, "")
+		return db.Scan(LIST, nil, count, false, "")
 	case "SET":
-		return db.SScan(nil, count, false, "")
+		return db.Scan(SET, nil, count, false, "")
 	case "ZSET":
-		return db.ZScan(nil, count, false, "")
+		return db.Scan(ZSET, nil, count, false, "")
 	default:
 		return nil, fmt.Errorf("invalid key type %s", tp)
 	}
diff --git a/server/cmd_replication_test.go b/server/cmd_replication_test.go
index 530d7db..66b99c7 100644
--- a/server/cmd_replication_test.go
+++ b/server/cmd_replication_test.go
@@ -14,8 +14,8 @@ func checkDataEqual(master *App, slave *App) error {
 	mdb, _ := master.ldb.Select(0)
 	sdb, _ := slave.ldb.Select(0)
 
-	mkeys, _ := mdb.Scan(nil, 100, true, "")
-	skeys, _ := sdb.Scan(nil, 100, true, "")
+	mkeys, _ := mdb.Scan(KV, nil, 100, true, "")
+	skeys, _ := sdb.Scan(KV, nil, 100, true, "")
 
 	if len(mkeys) != len(skeys) {
 		return fmt.Errorf("keys number not equal %d != %d", len(mkeys), len(skeys))
diff --git a/server/cmd_scan.go b/server/cmd_scan.go
new file mode 100644
index 0000000..e4f6f7f
--- /dev/null
+++ b/server/cmd_scan.go
@@ -0,0 +1,101 @@
+package server
+
+import (
+	"fmt"
+	"github.com/siddontang/go/hack"
+	"github.com/siddontang/ledisdb/ledis"
+	"strconv"
+	"strings"
+)
+
+// XSCAN type cursor [MATCH match] [COUNT count] [ASC|DESC]
+func xscanCommand(c *client) error {
+	args := c.args
+
+	if len(args) < 2 {
+		return ErrCmdParams
+	}
+
+	var dataType ledis.DataType
+	switch strings.ToUpper(hack.String(args[0])) {
+	case "KV":
+		dataType = ledis.KV
+	case "HASH":
+		dataType = ledis.HASH
+	case "LIST":
+		dataType = ledis.LIST
+	case "SET":
+		dataType = ledis.SET
+	case "ZSET":
+		dataType = ledis.ZSET
+	default:
+		return fmt.Errorf("invalid key type %s", args[0])
+	}
+
+	cursor := args[1]
+
+	args = args[2:]
+
+	match := ""
+	count := 10
+
+	desc := false
+
+	var err error
+
+	for i := 0; i < len(args); {
+		switch strings.ToUpper(hack.String(args[i])) {
+		case "MATCH":
+			if i+1 >= len(args) {
+				return ErrCmdParams
+			}
+
+			match = hack.String(args[i+1])
+			i = i + 2
+		case "COUNT":
+			if i+1 >= len(args) {
+				return ErrCmdParams
+			}
+
+			count, err = strconv.Atoi(hack.String(args[i+1]))
+			if err != nil {
+				return err
+			}
+
+			i = i + 2
+		case "ASC":
+			desc = false
+			i++
+		case "DESC":
+			desc = true
+			i++
+		default:
+			return fmt.Errorf("invalid argument %s", args[i])
+		}
+	}
+
+	var ay [][]byte
+	if !desc {
+		ay, err = c.db.Scan(dataType, cursor, count, false, match)
+	} else {
+		ay, err = c.db.RevScan(dataType, cursor, count, false, match)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	data := make([]interface{}, 2)
+	if len(ay) < count {
+		data[0] = []byte("")
+	} else {
+		data[0] = ay[len(ay)-1]
+	}
+	data[1] = ay
+	c.resp.writeArray(data)
+	return nil
+}
+
+func init() {
+	register("xscan", xscanCommand)
+}
diff --git a/server/scan_test.go b/server/cmd_scan_test.go
similarity index 81%
rename from server/scan_test.go
rename to server/cmd_scan_test.go
index 1778416..66d34d3 100644
--- a/server/scan_test.go
+++ b/server/cmd_scan_test.go
@@ -53,8 +53,8 @@ func checkScanValues(t *testing.T, ay interface{}, values ...int) {
 	}
 }
 
-func checkScan(t *testing.T, c *ledis.Client, cmd string) {
-	if ay, err := ledis.Values(c.Do(cmd, "", "count", 5)); err != nil {
+func checkScan(t *testing.T, c *ledis.Client, tp string) {
+	if ay, err := ledis.Values(c.Do("XSCAN", tp, "", "count", 5)); err != nil {
 		t.Fatal(err)
 	} else if len(ay) != 2 {
 		t.Fatal(len(ay))
@@ -64,7 +64,7 @@ func checkScan(t *testing.T, c *ledis.Client, cmd string) {
 		checkScanValues(t, ay[1], 0, 1, 2, 3, 4)
 	}
 
-	if ay, err := ledis.Values(c.Do(cmd, "4", "count", 6)); err != nil {
+	if ay, err := ledis.Values(c.Do("XSCAN", tp, "4", "count", 6)); err != nil {
 		t.Fatal(err)
 	} else if len(ay) != 2 {
 		t.Fatal(len(ay))
@@ -76,8 +76,8 @@ func checkScan(t *testing.T, c *ledis.Client, cmd string) {
 
 }
 
-func checkRevScan(t *testing.T, c *ledis.Client, cmd string) {
-	if ay, err := ledis.Values(c.Do(cmd, "", "count", 5)); err != nil {
+func checkRevScan(t *testing.T, c *ledis.Client, tp string) {
+	if ay, err := ledis.Values(c.Do("XSCAN", tp, "", "count", 5, "DESC")); err != nil {
 		t.Fatal(err)
 	} else if len(ay) != 2 {
 		t.Fatal(len(ay))
@@ -87,7 +87,7 @@ func checkRevScan(t *testing.T, c *ledis.Client, cmd string) {
 		checkScanValues(t, ay[1], 9, 8, 7, 6, 5)
 	}
 
-	if ay, err := ledis.Values(c.Do(cmd, "5", "count", 6)); err != nil {
+	if ay, err := ledis.Values(c.Do("XSCAN", tp, "5", "count", 6, "DESC")); err != nil {
 		t.Fatal(err)
 	} else if len(ay) != 2 {
 		t.Fatal(len(ay))
@@ -106,8 +106,8 @@ func testKVScan(t *testing.T, c *ledis.Client) {
 		}
 	}
 
-	checkScan(t, c, "xscan")
-	checkRevScan(t, c, "xrevscan")
+	checkScan(t, c, "KV")
+	checkRevScan(t, c, "KV")
 }
 
 func testHashScan(t *testing.T, c *ledis.Client) {
@@ -117,8 +117,8 @@ func testHashScan(t *testing.T, c *ledis.Client) {
 		}
 	}
 
-	checkScan(t, c, "xhscan")
-	checkRevScan(t, c, "xhrevscan")
+	checkScan(t, c, "HASH")
+	checkRevScan(t, c, "HASH")
 }
 
 func testListScan(t *testing.T, c *ledis.Client) {
@@ -128,8 +128,8 @@ func testListScan(t *testing.T, c *ledis.Client) {
 		}
 	}
 
-	checkScan(t, c, "xlscan")
-	checkRevScan(t, c, "xlrevscan")
+	checkScan(t, c, "LIST")
+	checkRevScan(t, c, "LIST")
 }
 
 func testZSetScan(t *testing.T, c *ledis.Client) {
@@ -139,8 +139,8 @@ func testZSetScan(t *testing.T, c *ledis.Client) {
 		}
 	}
 
-	checkScan(t, c, "zxscan")
-	checkRevScan(t, c, "zxrevscan")
+	checkScan(t, c, "ZSET")
+	checkRevScan(t, c, "ZSET")
 }
 
 func testSetScan(t *testing.T, c *ledis.Client) {
@@ -150,6 +150,6 @@ func testSetScan(t *testing.T, c *ledis.Client) {
 		}
 	}
 
-	checkScan(t, c, "xsscan")
-	checkRevScan(t, c, "xsrevscan")
+	checkScan(t, c, "SET")
+	checkRevScan(t, c, "SET")
 }
diff --git a/server/cmd_set.go b/server/cmd_set.go
index ae22bc5..b2ee2dc 100644
--- a/server/cmd_set.go
+++ b/server/cmd_set.go
@@ -262,14 +262,6 @@ func spersistCommand(c *client) error {
 	return nil
 }
 
-func sxscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.SScan)
-}
-
-func sxrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.SRevScan)
-}
-
 func xsexistsCommand(c *client) error {
 	args := c.args
 	if len(args) != 1 {
@@ -301,10 +293,6 @@ func init() {
 	register("sexpireat", sexpireAtCommand)
 	register("sttl", sttlCommand)
 	register("spersist", spersistCommand)
-	register("sxscan", sxscanCommand)
-	register("sxrevscan", sxrevscanCommand)
-	register("xsscan", sxscanCommand)
-	register("xsrevscan", sxrevscanCommand)
 	register("xsexists", xsexistsCommand)
 
 }
diff --git a/server/cmd_zset.go b/server/cmd_zset.go
index ddeefbd..77d2db3 100644
--- a/server/cmd_zset.go
+++ b/server/cmd_zset.go
@@ -641,14 +641,6 @@ func zinterstoreCommand(c *client) error {
 	return err
 }
 
-func zxscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.ZScan)
-}
-
-func zxrevscanCommand(c *client) error {
-	return xscanGeneric(c, c.db.ZRevScan)
-}
-
 func zparseMemberRange(minBuf []byte, maxBuf []byte) (min []byte, max []byte, rangeType uint8, err error) {
 	rangeType = store.RangeClose
 	if strings.ToLower(hack.String(minBuf)) == "-" {
@@ -815,9 +807,5 @@ func init() {
 	register("zexpireat", zexpireAtCommand)
 	register("zttl", zttlCommand)
 	register("zpersist", zpersistCommand)
-	register("zxscan", zxscanCommand)
-	register("zxrevscan", zxrevscanCommand)
-	register("xzscan", zxscanCommand)
-	register("xzrevscan", zxrevscanCommand)
 	register("xzexists", xzexistsCommand)
 }
diff --git a/server/const.go b/server/const.go
index dc55e24..9804ad7 100644
--- a/server/const.go
+++ b/server/const.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"errors"
+	"github.com/siddontang/ledisdb/ledis"
 )
 
 var (
@@ -26,12 +27,11 @@ var (
 )
 
 const (
-	KV = iota
-	LIST
-	HASH
-	SET
-	ZSET
-	BIT
+	KV   ledis.DataType = ledis.KV
+	LIST                = ledis.LIST
+	HASH                = ledis.HASH
+	SET                 = ledis.SET
+	ZSET                = ledis.ZSET
 )
 
 const (