ORACLE RAC 负载均衡与local_listener、remote_listener两个参数的配置关系
ORACLE RAC 负载均衡与local_listener、remote_listener两个参数的配置关系
 RAC的负载均衡主要由客户端和服务器端两种实现方式。
 
 1，客户端的实现，直接在tnsnames.ora中配置LOAD_BALANCE参数来实现。默认值是NO
 clinet_LB =
  (DESCRIPTION =
    (LOAD_BALANCE = YES)
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.4.124.243)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.4.124.244)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.4.124.245)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.4.124.246)(PORT = 1521))
    (CONNECT_DATA =
      (SERVICE_NAME = srv_epm1)
    )
  )
  2，服务器端的负载均衡LB设置。主要是通过两个初始化参数local_listener、remote_listener来实现的。通过这两个参数，oracle分别向这两个参数指向的listener进行注册，这样，listener就能知道各个服务的状态，进而进行连接分发。
  11gr2版本，这两个参数默认设置为如下

SQL> show parameter listener

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
listener_networks                    string
local_listener                       string      (DESCRIPTION=(ADDRESS_LIST=(AD
                                                 DRESS=(PROTOCOL=TCP)(HOST=10.4
                                                 .124.244)(PORT=1521))))
remote_listener                      string      dtydb-scan2:1521

由于以上设置，数据库实例分别向local_listener和remote_listener进行注册。

本地listener只注册了+ASM2和epmdb2两个实例

LSNRCTL> set current_listener LISTENER
Current Listener is LISTENER
LSNRCTL> service
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
Services Summary...
Service "+ASM" has 1 instance(s).
  Instance "+ASM2", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:10765 refused:0 state:ready
         LOCAL SERVER
Service "epmdb" has 1 instance(s).
  Instance "epmdb2", status READY, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:10 refused:0 state:ready
         LOCAL SERVER
The command completed successfully

SCAN listener注册了所有数据库实例默认service和运行在epmdb1实例上的服务srv_epm1
查看服务注册情况，SCAN

LSNRCTL> set current_listener LISTENER_SCAN1
Current Listener is LISTENER_SCAN1
LSNRCTL&