--ORACLE RAC TAF 配置（透明故障轉移）

TAF（Transparent Application Failover）即透明應用程式故障轉移技術。當初始化連線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)；
2：大致上TAF可以分為2種，連線時的TAF和會話建立後TAF；
3：TAF本身與是否RAC環境無關，但一般都用在RAC環境，最小程度的減少最應用的影響，單例項環境下也可以使用TAF，這樣使用PL/SQL developer連線資料庫，即使資料庫例項重啟，也不需要重新連線；
4：RAC環境下，還可以把TAF配置在伺服器端；
5：配置listener.ora檔案的GLOBAL_DBNAME引數後將會禁用TAF

檢視當前service

col name format a24
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'
select name, failover_method,failover_type, failover_retries,goal, clb_goal,aq_ha_notifications from dba_services;

1. 客戶端TAF配置

vi tnsnames.ora
NODE =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = rac-scan.yang.com)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = rac.yang.com)
(FAILOVER_MODE =
(TYPE = SELECT)
(METHOD = BASIC)
(RETRIES = 180)
(DELAY = 5))
)
)
SELECT MACHINE, FAILOVER_TYPE, FAILOVER_METHOD, FAILED_OVER FROM V$SESSION WHERE SID=141;
MACHINE TYPE METHOD FAI
-------------------- ---------- ----------- ---
tay SELECT BASIC NO

2. 伺服器端TAF配置

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
> 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

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

切換測試

--停服務
stop service -d cnposqa -s cnposqa_taf2
--服務啟動到instance 1
start service -d cnposqa -s cnposqa_taf2 -i cnposqa1

ORACLE RAC TAF 配置（透明故障轉移）

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