理论背景：

TAF（ Transparent Application Failover ） allows oracle clients to reconnect to a surviving instance in the event of a failure of the instance to which it is connected. There are two types of TAF available, SESSION and SELECT.

TAF允许oracle客户端重新连接到一个可持续的实例，当客户端连接的实例出现失败时。有2种有效的TAF类型，session and select 。有2种模式在TAF建立的故障转移连接，basic 和preconnect 。

session: 使用session方式，所有select查询相关的结果在重新建立新的连接后将全部丢失，需要重新发布select命令。

select:select：使用select方式，Oracle net会跟踪事务期间的所有select语句，并跟踪每一个与当前select相关的游标已返回多少行给客户 端。此时，假定select查询已返回500行，客户端当前连接的节点出现故障，Oracle Net自动建立连接到幸存的实例上并继续返回剩余的行数给客户端。假定总行数为1500，行，则1000行从剩余节点返回。

BASIC： 客户端通过地址列表成功建立连接后，即仅当客户端感知到节点故障时才创建到其他实例的连接

PRECONNECT: 预连接模式，是在最初建立连接时就同时建立到所有实例的连接，当发生故障时，立刻就可以切换到其他链路上

说明：上述两种方式适用于不同的情形，对于select方式，通常使用与OLAP数据库，而对于session方式则使用与OLTP数据库。因为 select 方式，Oracle 必须为每个session保存更多的内容，包括游标，用户上下文等，需要更多的资源。其次，两种方式期间所有未提交的DML事务将自动回滚且必须重启启动。alter session语句不会failover。临时对象不会failover也不能被重新启动。

配置Service-Side TAF 示例 （oracle用户操作）

1 创建TAF Service

node1-> pwd

/u01/app/11.2.0/grid/bin

node1-> ./srvctl add service -d devdb -s server_taf -r "devdb1" -P BASIC

说明：

Srvctl add service -d -s -r "preferred-instance-list" -a "available-instance-list" -P

srvctl add service中，只有perferred才会创建服务。 即在OCR中注册一个ora.raw.dmm.rac1.Srv的服务。

2 启动 server_taf服务

node1-> ./srvctl start service -d devdb -s server_taf

3 检查service 运行情况

node1-> ./srvctl config service -d devdb

Service name: server_taf

Service is enabled

Server pool: devdb_server_taf

Cardinality: 1

Disconnect: false

Service role: PRIMARY

Management policy: AUTOMATIC

DTP transaction: false

AQ HA notifications: false

Failover type: NONE

Failover method: NONE

TAF failover retries: 0

TAF failover delay: 0

Connection Load Balancing Goal: LONG

Runtime Load Balancing Goal: NONE

TAF policy specification: BASIC

Edition:

Preferred instances: devdb1

Available instances:

4 确认service ID

SQL> select name,service_id from dba_services where name = 'server_taf';

NAMESERVICE_ID

---------------------------------------------------------------- ----------

server_taf 3

5 给service 添加参数

SQL> execute dbms_service.modify_service (service_name => 'server_taf' -

, aq_ha_notifications => true -

, failover_method => dbms_service.failover_method_basic -

, failover_type => dbms_service.failover_type_select -

, failover_retries => 180 -

, failover_delay => 5 -

, clb_goal => dbms_service.clb_goal_long);

> > > > > >

PL/SQL procedure successfully completed.

6 确认参数修改

col name format a15

col failover_method format a11 heading 'METHOD'

col failover_type format a10 heading 'TYPE'

col failover_retries format 9999999 heading 'RETRIES'

col goal format a10

col clb_goal format a8

col AQ_HA_NOTIFICATIONS format a5 heading 'AQNOT'

SQL> select name, failover_method, failover_type, failover_retries,goal, clb_goal,aq_ha_notifications from dba_services where service_id = 3;

NAMEMETHOD TYPERETRIES GOAL CLB_GOAL AQNOT

--------------- ----------- ---------- -------- ---------- -------- -----

server_tafBASIC SELECT 180 NONE LONG YES

7 检查service 注册情况

node1-> lsnrctl services

LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 26-FEB-2017 04:43:55

Copyright (c) 1991, 2013, Oracle. All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))

Services Summary...

Service "+ASM" has 1 instance(s).

Instance "+ASM1", status READY, has 1 handler(s) for this service...

Handler(s):

"DEDICATED" established:2 refused:0 state:ready

LOCAL SERVER

Service "devdb" has 1 instance(s).

Instance "devdb1", status READY, has 1 handler(s) for this service...

Handler(s):

"DEDICATED" established:0 refused:0 state:ready

LOCAL SERVER

Service "devdbXDB" has 1 instance(s).

Instance "devdb1", status READY, has 1 handler(s) for this service...

Handler(s):

"D000" established:0 refused:0 current:0 max:1022 state:ready

DISPATCHER

(ADDRESS=(PROTOCOL=tcp)(HOST=node1.localdomain)(PORT=26677))

Service "server_taf" has 1 instance(s).

Instance "devdb1", status READY, has 1 handler(s) for this service...

Handler(s):

"DEDICATED" established:0 refused:0 state:ready

LOCAL SERVER

The command completed successfully

8 在客户端就可以使用Service-Side TAF了

​

在客户端TNS 配置：

server_taf =

(DESCRIPTION =

(ADDRESS = (PROTOCOL = TCP)(HOST = scan-cluster.localdomain)(PORT = 1521))

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME = server_taf)

)

)

连接测试

C:\Users\andy>sqlplus sys/oracle@10.100.25.8:1521/server_taf as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Sat Feb 25 20:59:41 2017

Copyright (c) 1982, 2014, Oracle. All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,

Data Mining and Real Application Testing options

9 停止service

node1-> ./srvctl stop service -d devdb -s server_taf -i devdb1

10 删除service

node1-> ./srvctl remove service -d devdb -s server_taf -i devdb1