diff --git a/Godeps/Godeps.json b/Godeps/Godeps.json
index 282164f..38c3bf1 100644
--- a/Godeps/Godeps.json
+++ b/Godeps/Godeps.json
@@ -60,7 +60,7 @@
 		},
 		{
 			"ImportPath": "github.com/siddontang/goredis",
-			"Rev": "f711beb9ecead18cf638a898610aa2c24ccb6dc7"
+			"Rev": "ca4c5d7500bcc6850c52824caf2c49a6015c8a03"
 		},
 		{
 			"ImportPath": "github.com/siddontang/rdb",
diff --git a/Godeps/_workspace/src/github.com/siddontang/goredis/client.go b/Godeps/_workspace/src/github.com/siddontang/goredis/client.go
index b9682a9..2ada1d9 100644
--- a/Godeps/_workspace/src/github.com/siddontang/goredis/client.go
+++ b/Godeps/_workspace/src/github.com/siddontang/goredis/client.go
@@ -5,6 +5,7 @@ import (
 	"net"
 	"strings"
 	"sync"
+	"time"
 )
 
 type PoolConn struct {
@@ -30,6 +31,9 @@ type Client struct {
 	password        string
 
 	conns *list.List
+
+	quit chan struct{}
+	wg   sync.WaitGroup
 }
 
 func getProto(addr string) string {
@@ -50,6 +54,10 @@ func NewClient(addr string, password string) *Client {
 	c.password = password
 
 	c.conns = list.New()
+	c.quit = make(chan struct{})
+
+	c.wg.Add(1)
+	go c.onCheck()
 
 	return c
 }
@@ -105,6 +113,9 @@ func (c *Client) Close() {
 	c.Lock()
 	defer c.Unlock()
 
+	close(c.quit)
+	c.wg.Wait()
+
 	for c.conns.Len() > 0 {
 		e := c.conns.Front()
 		co := e.Value.(*Conn)
@@ -142,11 +153,62 @@ func (c *Client) get() (co *Conn, err error) {
 
 func (c *Client) put(conn *Conn) {
 	c.Lock()
-	if c.conns.Len() >= c.maxIdleConns {
-		c.Unlock()
-		conn.Close()
+	defer c.Unlock()
+
+	for c.conns.Len() >= c.maxIdleConns {
+		// remove back
+		e := c.conns.Back()
+		co := e.Value.(*Conn)
+		c.conns.Remove(e)
+
+		co.Close()
+	}
+
+	c.conns.PushFront(conn)
+}
+
+func (c *Client) getIdle() *Conn {
+	c.Lock()
+	defer c.Unlock()
+
+	if c.conns.Len() == 0 {
+		return nil
 	} else {
-		c.conns.PushFront(conn)
-		c.Unlock()
+		e := c.conns.Back()
+		co := e.Value.(*Conn)
+		c.conns.Remove(e)
+		return co
+	}
+}
+
+func (c *Client) checkIdle() {
+	co := c.getIdle()
+	if co == nil {
+		return
+	}
+
+	_, err := co.Do("PING")
+	if err != nil {
+		co.Close()
+	} else {
+		c.put(co)
+	}
+}
+
+func (c *Client) onCheck() {
+	t := time.NewTicker(3 * time.Second)
+
+	defer func() {
+		t.Stop()
+		c.wg.Done()
+	}()
+
+	for {
+		select {
+		case <-t.C:
+			c.checkIdle()
+		case <-c.quit:
+			return
+		}
 	}
 }
diff --git a/cmd/ledis-server/main.go b/cmd/ledis-server/main.go
index 594a046..7987733 100644
--- a/cmd/ledis-server/main.go
+++ b/cmd/ledis-server/main.go
@@ -26,6 +26,7 @@ var readonly = flag.Bool("readonly", false, "set readonly mode, slave server is
 var rpl = flag.Bool("rpl", false, "enable replication or not, slave server is always enabled")
 var rplSync = flag.Bool("rpl_sync", false, "enable sync replication or not")
 var ttlCheck = flag.Int("ttl_check", 0, "TTL check interval")
+var databases = flag.Int("databases", 0, "ledisdb maximum database number")
 
 func main() {
 	runtime.GOMAXPROCS(runtime.NumCPU())
@@ -59,23 +60,27 @@ func main() {
 		cfg.DBName = *dbName
 	}
 
+	if *databases > 0 {
+		cfg.Databases = *databases
+	}
+
+	// check bool flag, use it.
+	for _, arg := range os.Args {
+		arg := strings.ToLower(arg)
+		switch arg {
+		case "-rpl", "-rpl=true", "-rpl=false":
+			cfg.UseReplication = *rpl
+		case "-readonly", "-readonly=true", "-readonly=false":
+			cfg.Readonly = *readonly
+		case "-rpl_sync", "-rpl_sync=true", "-rpl_sync=false":
+			cfg.Replication.Sync = *rplSync
+		}
+	}
+
 	if len(*slaveof) > 0 {
 		cfg.SlaveOf = *slaveof
 		cfg.Readonly = true
 		cfg.UseReplication = true
-	} else {
-		cfg.Readonly = *readonly
-
-		// if rpl in command flag, use it.
-		for _, arg := range os.Args {
-			arg := strings.ToLower(arg)
-			if arg == "-rpl" || arg == "-rpl=true" || arg == "-rpl=false" {
-				cfg.UseReplication = *rpl
-				break
-			}
-		}
-
-		cfg.Replication.Sync = *rplSync
 	}
 
 	if *ttlCheck > 0 {
diff --git a/config/config.toml b/config/config.toml
index 0b965f5..6135848 100644
--- a/config/config.toml
+++ b/config/config.toml
@@ -11,7 +11,7 @@ data_dir = "/tmp/ledis_server"
 
 # Set the number of databases. You can use `select dbindex` to choose a db.
 # dbindex must be in [0, databases - 1].
-# Maximum databases is 16 now. 
+# Default databases is 16, maximum is 10240 now.
 databases = 16
 
 # Log server command, set empty to disable
diff --git a/etc/ledis.conf b/etc/ledis.conf
index 0b965f5..6135848 100644
--- a/etc/ledis.conf
+++ b/etc/ledis.conf
@@ -11,7 +11,7 @@ data_dir = "/tmp/ledis_server"
 
 # Set the number of databases. You can use `select dbindex` to choose a db.
 # dbindex must be in [0, databases - 1].
-# Maximum databases is 16 now. 
+# Default databases is 16, maximum is 10240 now.
 databases = 16
 
 # Log server command, set empty to disable
diff --git a/ledis/ledis.go b/ledis/ledis.go
index 01e0977..7397f2a 100644
--- a/ledis/ledis.go
+++ b/ledis/ledis.go
@@ -48,8 +48,8 @@ func Open(cfg *config.Config) (*Ledis, error) {
 
 	if cfg.Databases == 0 {
 		cfg.Databases = 16
-	} else if cfg.Databases > 16 {
-		cfg.Databases = 16
+	} else if cfg.Databases > MaxDatabases {
+		cfg.Databases = MaxDatabases
 	}
 
 	os.MkdirAll(cfg.DataDir, 0755)
@@ -112,8 +112,8 @@ func (l *Ledis) Close() {
 }
 
 func (l *Ledis) Select(index int) (*DB, error) {
-	if index < 0 || index >= MaxDatabases {
-		return nil, fmt.Errorf("invalid db index %d, must in [0, %d]", index, MaxDatabases-1)
+	if index < 0 || index >= l.cfg.Databases {
+		return nil, fmt.Errorf("invalid db index %d, must in [0, %d]", index, l.cfg.Databases-1)
 	}
 
 	l.dbLock.Lock()
diff --git a/ledis/ledis_test.go b/ledis/ledis_test.go
index a0c9879..de308e7 100644
--- a/ledis/ledis_test.go
+++ b/ledis/ledis_test.go
@@ -14,6 +14,7 @@ func getTestDB() *DB {
 	f := func() {
 		cfg := config.NewConfigDefault()
 		cfg.DataDir = "/tmp/test_ledis"
+		cfg.Databases = 10240
 
 		os.RemoveAll(cfg.DataDir)
 
diff --git a/server/client_resp.go b/server/client_resp.go
index 6d493f9..eabc357 100644
--- a/server/client_resp.go
+++ b/server/client_resp.go
@@ -134,6 +134,11 @@ func (c *respClient) run() {
 		reqData, err := c.readRequest()
 		if err == nil {
 			err = c.handleRequest(reqData)
+
+			c.cmd = ""
+			c.args = nil
+
+			c.ar.Reset()
 		}
 
 		if err != nil {
@@ -154,6 +159,16 @@ func (c *respClient) handleRequest(reqData [][]byte) error {
 		c.cmd = hack.String(lowerSlice(reqData[0]))
 		c.args = reqData[1:]
 	}
+
+	if c.cmd == "xselect" {
+		err := c.handleXSelectCmd()
+		if err != nil {
+			c.resp.writeError(err)
+			c.resp.flush()
+			return nil
+		}
+	}
+
 	if c.cmd == "quit" {
 		c.activeQuit = true
 		c.resp.writeStatus(OK)
@@ -164,10 +179,35 @@ func (c *respClient) handleRequest(reqData [][]byte) error {
 
 	c.perform()
 
-	c.cmd = ""
-	c.args = nil
+	return nil
+}
 
-	c.ar.Reset()
+// XSELECT db THEN command
+func (c *respClient) handleXSelectCmd() error {
+	if len(c.args) <= 2 {
+		// invalid command format
+		return fmt.Errorf("invalid format for XSELECT, must XSELECT db THEN your command")
+	}
+
+	if hack.String(upperSlice(c.args[1])) != "THEN" {
+		// invalid command format, just resturn here
+		return fmt.Errorf("invalid format for XSELECT, must XSELECT db THEN your command")
+	}
+
+	index, err := strconv.Atoi(hack.String(c.args[0]))
+	if err != nil {
+		return fmt.Errorf("invalid db for XSELECT, err %v", err)
+	}
+
+	db, err := c.app.ldb.Select(index)
+	if err != nil {
+		return fmt.Errorf("invalid db for XSELECT, err %v", err)
+	}
+
+	c.db = db
+
+	c.cmd = hack.String(lowerSlice(c.args[2]))
+	c.args = c.args[3:]
 
 	return nil
 }
diff --git a/server/cmd_server_test.go b/server/cmd_server_test.go
new file mode 100644
index 0000000..ca283dc
--- /dev/null
+++ b/server/cmd_server_test.go
@@ -0,0 +1,38 @@
+package server
+
+import (
+	"github.com/siddontang/goredis"
+	"testing"
+)
+
+func TestXSelect(t *testing.T) {
+	c1 := getTestConn()
+	defer c1.Close()
+
+	c2 := getTestConn()
+	defer c2.Close()
+
+	_, err := c1.Do("XSELECT", "1", "THEN", "SET", "tmp_select_key", "1")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = goredis.Int(c2.Do("GET", "tmp_select_key"))
+	if err != goredis.ErrNil {
+		t.Fatal(err)
+	}
+
+	n, _ := goredis.Int(c2.Do("XSELECT", "1", "THEN", "GET", "tmp_select_key"))
+	if n != 1 {
+		t.Fatal(n)
+	}
+
+	n, _ = goredis.Int(c2.Do("GET", "tmp_select_key"))
+	if n != 1 {
+		t.Fatal(n)
+	}
+
+	c1.Do("SELECT", 0)
+	c2.Do("SELECT", 0)
+
+}
diff --git a/server/util.go b/server/util.go
index 7c5b73d..a6ef5d4 100644
--- a/server/util.go
+++ b/server/util.go
@@ -134,3 +134,14 @@ func lowerSlice(buf []byte) []byte {
 	}
 	return buf
 }
+
+func upperSlice(buf []byte) []byte {
+	for i, r := range buf {
+		if 'a' <= r && r <= 'z' {
+			r -= 'a' - 'A'
+		}
+
+		buf[i] = r
+	}
+	return buf
+}