diff --git a/conf.sample.yml b/conf.sample.yml
index 9d736fd..6c5919f 100644
--- a/conf.sample.yml
+++ b/conf.sample.yml
@@ -35,7 +35,7 @@ Store: # specify which engine to store trans status
 # TimeoutToFail: 35 # timeout for XA, TCC to fail. saga's timeout default to infinite, which can be overwritten in saga options
 # RetryInterval: 10 # the subtrans branch will be retried after this interval
 
-### db config of examples
+### dtm can run examples, and examples will use following config to connect db
 ExamplesDB:
   Driver: 'mysql'
   Host: 'localhost'
diff --git a/dtmcli/dtmimp/db_special.go b/dtmcli/dtmimp/db_special.go
index 3eb3071..d45f460 100644
--- a/dtmcli/dtmimp/db_special.go
+++ b/dtmcli/dtmimp/db_special.go
@@ -13,7 +13,6 @@ import (
 
 // DBSpecial db specific operations
 type DBSpecial interface {
-	TimestampAdd(second int) string
 	GetPlaceHoldSQL(sql string) string
 	GetInsertIgnoreTemplate(tableAndValues string, pgConstraint string) string
 	GetXaSQL(command string, xid string) string
@@ -24,10 +23,6 @@ var currentDBType = DBTypeMysql
 
 type mysqlDBSpecial struct{}
 
-func (*mysqlDBSpecial) TimestampAdd(second int) string {
-	return fmt.Sprintf("date_add(now(), interval %d second)", second)
-}
-
 func (*mysqlDBSpecial) GetPlaceHoldSQL(sql string) string {
 	return sql
 }
diff --git a/dtmcli/dtmimp/db_special_test.go b/dtmcli/dtmimp/db_special_test.go
index 3bf7012..3966cd2 100644
--- a/dtmcli/dtmimp/db_special_test.go
+++ b/dtmcli/dtmimp/db_special_test.go
@@ -22,13 +22,11 @@ func TestDBSpecial(t *testing.T) {
 
 	assert.Equal(t, "? ?", sp.GetPlaceHoldSQL("? ?"))
 	assert.Equal(t, "xa start 'xa1'", sp.GetXaSQL("start", "xa1"))
-	assert.Equal(t, "date_add(now(), interval 1000 second)", sp.TimestampAdd(1000))
 	assert.Equal(t, "insert ignore into a(f) values(?)", sp.GetInsertIgnoreTemplate("a(f) values(?)", "c"))
 	SetCurrentDBType(DBTypePostgres)
 	sp = GetDBSpecial()
 	assert.Equal(t, "$1 $2", sp.GetPlaceHoldSQL("? ?"))
 	assert.Equal(t, "begin", sp.GetXaSQL("start", "xa1"))
-	assert.Equal(t, "current_timestamp + interval '1000 second'", sp.TimestampAdd(1000))
 	assert.Equal(t, "insert into a(f) values(?) on conflict ON CONSTRAINT c do nothing", sp.GetInsertIgnoreTemplate("a(f) values(?)", "c"))
 	SetCurrentDBType(old)
 }
diff --git a/dtmsvr/storage/sql.go b/dtmsvr/storage/sql.go
index 324eddd..61e8862 100644
--- a/dtmsvr/storage/sql.go
+++ b/dtmsvr/storage/sql.go
@@ -112,7 +112,12 @@ func (s *SqlStore) TouchCronTime(global *TransGlobalStore, nextCronInterval int6
 
 func (s *SqlStore) LockOneGlobalTrans(expireIn time.Duration) *TransGlobalStore {
 	db := dbGet()
-	getTime := dtmimp.GetDBSpecial().TimestampAdd
+	getTime := func(second int) string {
+		return map[string]string{
+			"mysql":    fmt.Sprintf("date_add(now(), interval %d second)", second),
+			"postgres": fmt.Sprintf("current_timestamp + interval '%d second'", second),
+		}[config.Store.Driver]
+	}
 	expire := int(expireIn / time.Second)
 	whereTime := fmt.Sprintf("next_cron_time < %s", getTime(expire))
 	owner := uuid.NewString()