diff --git a/database/gdb/gdb.go b/database/gdb/gdb.go
index b3e355c64..67a1489af 100644
--- a/database/gdb/gdb.go
+++ b/database/gdb/gdb.go
@@ -233,13 +233,14 @@ type (
 )
 
 const (
-	gINSERT_OPTION_DEFAULT       = 0
-	gINSERT_OPTION_REPLACE       = 1
-	gINSERT_OPTION_SAVE          = 2
-	gINSERT_OPTION_IGNORE        = 3
-	gDEFAULT_BATCH_NUM           = 10 // Per count for batch insert/replace/save
-	gDEFAULT_CONN_MAX_IDLE_COUNT = 10 // Max idle connection count in pool.
-	gDEFAULT_CONN_MAX_LIFE_TIME  = 30 // Max life time for per connection in pool in seconds.
+	insertOptionDefault     = 0
+	insertOptionReplace     = 1
+	insertOptionSave        = 2
+	insertOptionIgnore      = 3
+	defaultBatchNumber      = 10  // Per count for batch insert/replace/save.
+	defaultMaxIdleConnCount = 10  // Max idle connection count in pool.
+	defaultMaxOpenConnCount = 100 // Max open connection count in pool.
+	defaultMaxConnLifeTime  = 30  // Max life time for per connection in pool in seconds.
 )
 
 var (
@@ -310,8 +311,9 @@ func New(group ...string) (db DB, err error) {
 				logger:           glog.New(),
 				prefix:           node.Prefix,
 				config:           node,
-				maxIdleConnCount: gDEFAULT_CONN_MAX_IDLE_COUNT,
-				maxConnLifetime:  gDEFAULT_CONN_MAX_LIFE_TIME, // Default max connection life time if user does not configure.
+				maxIdleConnCount: defaultMaxIdleConnCount,
+				maxOpenConnCount: defaultMaxOpenConnCount,
+				maxConnLifetime:  defaultMaxConnLifeTime, // Default max connection life time if user does not configure.
 			}
 			if v, ok := driverMap[node.Type]; ok {
 				c.DB, err = v.New(c, node)
diff --git a/database/gdb/gdb_core.go b/database/gdb/gdb_core.go
index af89f54d3..58058204d 100644
--- a/database/gdb/gdb_core.go
+++ b/database/gdb/gdb_core.go
@@ -452,7 +452,7 @@ func (c *Core) DoInsert(link Link, table string, data interface{}, option int, b
 		values = append(values, "?")
 		params = append(params, v)
 	}
-	if option == gINSERT_OPTION_SAVE {
+	if option == insertOptionSave {
 		for k, _ := range dataMap {
 			// If it's SAVE operation,
 			// do not automatically update the creating time.
@@ -599,7 +599,7 @@ func (c *Core) DoBatchInsert(link Link, table string, list interface{}, option i
 		operation      = GetInsertOperationByOption(option)
 		updateStr      = ""
 	)
-	if option == gINSERT_OPTION_SAVE {
+	if option == insertOptionSave {
 		for _, k := range keys {
 			// If it's SAVE operation,
 			// do not automatically update the creating time.
@@ -617,7 +617,7 @@ func (c *Core) DoBatchInsert(link Link, table string, list interface{}, option i
 		}
 		updateStr = fmt.Sprintf("ON DUPLICATE KEY UPDATE %s", updateStr)
 	}
-	batchNum := gDEFAULT_BATCH_NUM
+	batchNum := defaultBatchNumber
 	if len(batch) > 0 && batch[0] > 0 {
 		batchNum = batch[0]
 	}
diff --git a/database/gdb/gdb_driver_oracle.go b/database/gdb/gdb_driver_oracle.go
index 181d25fa8..c9862a6a4 100644
--- a/database/gdb/gdb_driver_oracle.go
+++ b/database/gdb/gdb_driver_oracle.go
@@ -248,7 +248,7 @@ func (d *DriverOracle) DoInsert(link Link, table string, data interface{}, optio
 	indexs := make([]string, 0)
 	indexMap := make(map[string]string)
 	indexExists := false
-	if option != gINSERT_OPTION_DEFAULT {
+	if option != insertOptionDefault {
 		index, err := d.getTableUniqueIndex(table)
 		if err != nil {
 			return nil, err
@@ -276,7 +276,7 @@ func (d *DriverOracle) DoInsert(link Link, table string, data interface{}, optio
 		k = strings.ToUpper(k)
 
 		// 操作类型为REPLACE/SAVE时且存在唯一索引才使用merge，否则使用insert
-		if (option == gINSERT_OPTION_REPLACE || option == gINSERT_OPTION_SAVE) && indexExists {
+		if (option == insertOptionReplace || option == insertOptionSave) && indexExists {
 			fields = append(fields, tableAlias1+"."+charL+k+charR)
 			values = append(values, tableAlias2+"."+charL+k+charR)
 			params = append(params, v)
@@ -302,18 +302,18 @@ func (d *DriverOracle) DoInsert(link Link, table string, data interface{}, optio
 		}
 	}
 
-	if indexExists && option != gINSERT_OPTION_DEFAULT {
+	if indexExists && option != insertOptionDefault {
 		switch option {
-		case gINSERT_OPTION_REPLACE:
+		case insertOptionReplace:
 			fallthrough
-		case gINSERT_OPTION_SAVE:
+		case insertOptionSave:
 			tmp := fmt.Sprintf(
 				"MERGE INTO %s %s USING(SELECT %s FROM DUAL) %s ON(%s) WHEN MATCHED THEN UPDATE SET %s WHEN NOT MATCHED THEN INSERT (%s) VALUES(%s)",
 				table, tableAlias1, strings.Join(subSqlStr, ","), tableAlias2,
 				strings.Join(onStr, "AND"), strings.Join(updateStr, ","), strings.Join(fields, ","), strings.Join(values, ","),
 			)
 			return d.DB.DoExec(link, tmp, params...)
-		case gINSERT_OPTION_IGNORE:
+		case insertOptionIgnore:
 			return d.DB.DoExec(link,
 				fmt.Sprintf(
 					"INSERT /*+ IGNORE_ROW_ON_DUPKEY_INDEX(%s(%s)) */ INTO %s(%s) VALUES(%s)",
@@ -391,7 +391,7 @@ func (d *DriverOracle) DoBatchInsert(link Link, table string, list interface{},
 	valueHolderStr := strings.Join(holders, ",")
 
 	// 当操作类型非insert时调用单笔的insert功能
-	if option != gINSERT_OPTION_DEFAULT {
+	if option != insertOptionDefault {
 		for _, v := range listMap {
 			r, err := d.DB.DoInsert(link, table, v, option, 1)
 			if err != nil {
@@ -409,7 +409,7 @@ func (d *DriverOracle) DoBatchInsert(link Link, table string, list interface{},
 	}
 
 	// 构造批量写入数据格式(注意map的遍历是无序的)
-	batchNum := gDEFAULT_BATCH_NUM
+	batchNum := defaultBatchNumber
 	if len(batch) > 0 {
 		batchNum = batch[0]
 	}
diff --git a/database/gdb/gdb_func.go b/database/gdb/gdb_func.go
index 24adb348d..03de4496c 100644
--- a/database/gdb/gdb_func.go
+++ b/database/gdb/gdb_func.go
@@ -88,9 +88,9 @@ func ListItemValuesUnique(list interface{}, key string, subKey ...interface{}) [
 func GetInsertOperationByOption(option int) string {
 	var operator string
 	switch option {
-	case gINSERT_OPTION_REPLACE:
+	case insertOptionReplace:
 		operator = "REPLACE"
-	case gINSERT_OPTION_IGNORE:
+	case insertOptionIgnore:
 		operator = "INSERT IGNORE"
 	default:
 		operator = "INSERT"
diff --git a/database/gdb/gdb_model_insert.go b/database/gdb/gdb_model_insert.go
index 1007b78da..8ccb55d28 100644
--- a/database/gdb/gdb_model_insert.go
+++ b/database/gdb/gdb_model_insert.go
@@ -101,7 +101,7 @@ func (m *Model) Insert(data ...interface{}) (result sql.Result, err error) {
 	if len(data) > 0 {
 		return m.Data(data...).Insert()
 	}
-	return m.doInsertWithOption(gINSERT_OPTION_DEFAULT, data...)
+	return m.doInsertWithOption(insertOptionDefault, data...)
 }
 
 // InsertIgnore does "INSERT IGNORE INTO ..." statement for the model.
@@ -111,7 +111,7 @@ func (m *Model) InsertIgnore(data ...interface{}) (result sql.Result, err error)
 	if len(data) > 0 {
 		return m.Data(data...).Insert()
 	}
-	return m.doInsertWithOption(gINSERT_OPTION_IGNORE, data...)
+	return m.doInsertWithOption(insertOptionIgnore, data...)
 }
 
 // Replace does "REPLACE INTO ..." statement for the model.
@@ -121,7 +121,7 @@ func (m *Model) Replace(data ...interface{}) (result sql.Result, err error) {
 	if len(data) > 0 {
 		return m.Data(data...).Replace()
 	}
-	return m.doInsertWithOption(gINSERT_OPTION_REPLACE, data...)
+	return m.doInsertWithOption(insertOptionReplace, data...)
 }
 
 // Save does "INSERT INTO ... ON DUPLICATE KEY UPDATE..." statement for the model.
@@ -134,7 +134,7 @@ func (m *Model) Save(data ...interface{}) (result sql.Result, err error) {
 	if len(data) > 0 {
 		return m.Data(data...).Save()
 	}
-	return m.doInsertWithOption(gINSERT_OPTION_SAVE, data...)
+	return m.doInsertWithOption(insertOptionSave, data...)
 }
 
 // doInsertWithOption inserts data with option parameter.
@@ -155,7 +155,7 @@ func (m *Model) doInsertWithOption(option int, data ...interface{}) (result sql.
 	)
 	// Batch operation.
 	if list, ok := m.data.(List); ok {
-		batch := gDEFAULT_BATCH_NUM
+		batch := defaultBatchNumber
 		if m.batch > 0 {
 			batch = m.batch
 		}