原文地址：http://blog.itpub.net/17086096/viewspace-1872783/

TAF（Transparent Application Failover）即透明應用程式故障轉移技術。當初始化連接出現問題無法連線時，該功能可以保證應用程式重新連線到可用服務。在重新連線過程中，之前的活動事務將會被回滾，但在“具體條件”下TAF可以保證SELECT語句不被終止。這也是RAC亮點之一。

所謂的“具體條件”指的就是FAILOVER_MODE中METHOD選擇“BASIC”、TYPE選擇“SELECT”

TAF的特性：
1：TAF是ORACLE客戶端提供的一項特性，使用TAF，對客戶端的環境有一定的要求，比如JAVA的JDBC驅動、Oracle客戶端的版本等（8i開始支援TAF)；

檢視當前service

1. col name format a24
   
2. col failover_method format a11 heading 'METHOD' 
   
3. col failover_type format a10 heading 'TYPE'
    
   
4. col failover_retries format 9999999 heading 'RETRIES' 
   
5. col goal format a10 
   
6. col clb_goal format a8 
   
7. col AQ_HA_NOTIFICATIONS format a5 heading 'AQNOT' 
   
8. select name, failover_method,failover_type, failover_retries,goal, clb_goal,aq_ha_notifications from dba_services;

1. 客戶端TAF配置

1. vi tnsnames.ora 
   
2. NODE = 
   
3.   (DESCRIPTION =
    
   
4.     (ADDRESS_LIST = 
   
5.       (ADDRESS = (PROTOCOL = TCP)(HOST = rac-scan.yang.com)(PORT = 1521)) 
   
6.     ) 
   
7.     (CONNECT_DATA = 
   
8.       (SERVICE_NAME = rac.yang.com) 
   
9.       (FAILOVER_MODE = 
   
10.        (TYPE = SELECT) 
    
11.        (METHOD = BASIC) 
    
12.        (RETRIES = 180) 
    
13.        (DELAY = 5)) 
    
14.     ) 
    
15.   )
    
    
16. SELECT MACHINE, FAILOVER_TYPE, FAILOVER_METHOD, FAILED_OVER FROM V$SESSION WHERE SID=141;  
    
17. MACHINE TYPE METHOD FAI  
    -------------------- ---------- ----------- ---  
    tay SELECT BASIC NO

2.1新增taf服務
srvctl add service -d cnposqa -s cnposqa_taf -r "cnposqa1,cnposqa2" -P BASIC

    -e        Failover type (NONE, SESSION, or SELECT)
    -m      Failover method (NONE or BASIC)
    srvctl add service -d cnposqa -s cnposqa_taftt -r "cnposqa1,cnposqa2" -e select -m basic -P BASIC

2.2啟動服務
srvctl start service -d cnposqa -s cnposqa_taf

2.3檢查服務情況
[email protected]_rel:/oradata/> srvctl config service -d cnposqa -s cnposqa_taf
Service name: cnposqa_taf
Service is enabled
Server pool: cnposqa_cnposqa_taf
Cardinality: 2
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: cnposqa1,cnposqa2
Available instances:

2.3 給service新增引數(basic,select)：

execute dbms_service.modify_service (service_name => 'cnposqa_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);

++單邊服務新增

--cnposqa_taf2單邊服務，主節點cnposqa2, 副節點cnposqa1   (-r Preferred  , -a Available )
srvctl add service -d cnposqa -s cnposqa_taf2 -r "cnposqa2" -a "cnposqa1" -P BASIC

[email protected]:/oradata> srvctl config service -d cnposqa -s cnposqa_taf2 
Service name: cnposqa_taf2
Service is enabled
Server pool: cnposqa_cnposqa_taf2
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: cnposqa2
Available instances: cnposqa1

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