这里不鏖述remote_listener参数的作用和服务器端连接时负载均衡的技术，只说明以下本次演示，想说明的是客户端连接原始LISTENER时只发生短暂的通信即断开，继而连接由初始连接节点分配的目标节点的LISTENER，且保持对监听端口之间的通信connection，这里在Unix/Linux上只用到监听端口，原理如下图：
我们通过client sql net trace来连接一些详细信息：
SQL> select instance_name,instance_number from gv$instance; INSTANCE_NAME INSTANCE_NUMBER ---------------- --------------- VPROD2 2 VPROD1 1 SQL> show parameter remote_listener NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ remote_listener string RAC_LISTENER [grid@vrh1 admin]$ tnsping RAC_LISTENER TNS Ping Utility for Linux: Version 11.2.0.3.0 - Production on 06-SEP-2012 08:15:42 Copyright (c) 1997, 2011, Oracle. All rights reserved. Used parameter files: /g01/11.2.0/grid/network/admin/sqlnet.ora Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = vrh1-vip)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = vrh2-vip)(PORT = 1521))) OK (10 msec) 从远程节点使用TNSNAMES连接1节点实例， 由于remote_listener 的server-side connect load balancing ，会分发到2节点上 通过设置SQLNET.ORA中的参数做client sql net trace [oracle@nas sqlnet]$ tnsping SERVER TNS Ping Utility for Linux: Version 11.2.0.3.0 - Production on 06-SEP-2012 13:16:48 Copyright (c) 1997, 2011, Oracle. All rights reserved. Used parameter files: /s01/orabase/product/11.2.0/dbhome_1/network/admin/sqlnet.ora Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = vrh1-vip)(PORT = 1521)) (CONNECT_DATA = (SERVICE_NAME = VPROD))) OK (10 msec) [oracle@nas sqlnet]$ sqlplus system/oracle@SERVER SQL*Plus: Release 11.2.0.3.0 Production on Thu Sep 6 13:17:25 2012 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP, Data Mining and Real Application Testing options INSTANCE_NAME ---------------- VPROD2
以上利用remote_listener服务器端负载均衡成功由1及节点的listener路由到2节点上的LISTENER，并创建server process，我们来观察
SQL NET TRACE
(890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 00 00 28 44 45 53 43 52 |..(DESCR| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 49 50 54 49 4F 4E 3D 28 |IPTION=(| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 43 4F 4E 4E 45 43 54 5F |CONNECT_| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 44 41 54 41 3D 28 53 45 |DATA=(SE| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 52 56 49 43 45 5F 4E 41 |RVICE_NA| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 4D 45 3D 56 50 52 4F 44 |ME=VPROD| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 29 28 43 49 44 3D 28 50 |)(CID=(P| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 52 4F 47 52 41 4D 3D 73 |ROGRAM=s| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 71 6C 70 6C 75 73 29 28 |qlplus)(| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 48 4F 53 54 3D 6E 61 73 |HOST=nas| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 2E 6F 72 61 63 6C 65 2E |.oracle.| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 63 6F 6D 29 28 55 53 45 |com)(USE| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 52 3D 6F 72 61 63 6C 65 |R=oracle| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 29 29 28 53 45 52 56 45 |))(SERVE| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 52 3D 64 65 64 69 63 61 |R=dedica| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 74 65 64 29 28 49 4E 53 |ted)(INS| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 54 41 4E 43 45 5F 4E 41 |TANCE_NA| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 4D 45 3D 56 50 52 4F 44 |ME=VPROD| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 32 29 29 28 41 44 44 52 |2))(ADDR| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 45 53 53 3D 28 50 52 4F |ESS=(PRO| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 54 4F 43 4F 4C 3D 54 43 |TOCOL=TC| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 50 29 28 48 4F 53 54 3D |P)(HOST=| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 31 39 32 2E 31 36 38 2E |192.168.| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 31 2E 31 36 32 29 28 50 |1.162)(P| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 4F 52 54 3D 31 35 32 31 |ORT=1521| (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 29 29 29 |))) | (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: 259 bytes to transport (890354416) [000001 06-SEP-2012 13:29:11:567] nspsend: normal exit (890354416) [000001 06-SEP-2012 13:29:11:567] nscon: exit (0) (890354416) [000001 06-SEP-2012 13:29:11:567] snsbitts_ts: entry (890354416) [000001 06-SEP-2012 13:29:11:567] snsbitts_ts: acquired the bit (890354416) [000001 06-SEP-2012 13:29:11:567] snsbitts_ts: normal exit ................ (890354416) [000001 06-SEP-2012 13:29:11:560] snsbitcl_ts: normal exit (890354416) [000001 06-SEP-2012 13:29:11:560] nsmfr: entry (890354416) [000001 06-SEP-2012 13:29:11:560] nsmfr: 2760 bytes at 0x10a57910 (890354416) [000001 06-SEP-2012 13:29:11:560] nsmfr: normal exit (890354416) [000001 06-SEP-2012 13:29:11:561] snsbitcl_ts: entry (890354416) [000001 06-SEP-2012 13:29:11:561] snsbitcl_ts: normal exit (890354416) [000001 06-SEP-2012 13:29:11:561] nsmfr: entry (890354416) [000001 06-SEP-2012 13:29:11:561] nsmfr: 1528 bytes at 0x10a57310 (890354416) [000001 06-SEP-2012 13:29:11:561] nsmfr: normal exit (890354416) [000001 06-SEP-2012 13:29:11:561] nsclose: normal exit (890354416) [000001 06-SEP-2012 13:29:11:561] nscall: connecting... (890354416) [000001 06-SEP-2012 13:29:11:561] nsc2addr: entry (890354416) [000001 06-SEP-2012 13:29:11:561] nsc2addr: (ADDRESS=(PROTOCOL=TCP)(HOST=vrh2.oracle.com)(PORT=1521)) (890354416) [000001 06-SEP-2012 13:29:11:561] nttbnd2addr: entry (890354416) [000001 06-SEP-2012 13:29:11:561] snlinGetAddrInfo: entry (890354416) [000001 06-SEP-2012 13:29:11:561] snlinGetAddrInfo: getaddrinfo() failed with error -2 (890354416) [000001 06-SEP-2012 13:29:11:561] snlinGetAddrInfo: exit (890354416) [000001 06-SEP-2012 13:29:11:561] nttbnd2addr: looking up IP addr for host: vrh2.oracle.com (890354416) [000001 06-SEP-2012 13:29:11:561] snlinGetAddrInfo: entry (890354416) [000001 06-SEP-2012 13:29:11:561] snlinGetAddrInfo: exit (890354416) [000001 06-SEP-2012 13:29:11:561] snlinFreeAddrInfo: entry (890354416) [000001 06-SEP-2012 13:29:11:561] snlinFreeAddrInfo: exit (890354416) [000001 06-SEP-2012 13:29:11:561] nttbnd2addr: exit
通过netstat 可以查看当前client远程连接的端口，可以看到已经与1节点断开了connection:
[root@nas ~]# netstat -anp Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:2208 0.0.0.0:* LISTEN 2959/hpiod tcp 0 0 127.0.0.1:199 0.0.0.0:* LISTEN 5424/snmpd tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 2526/portmap tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 5396/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 3000/cupsd tcp 0 0 0.0.0.0:632 0.0.0.0:* LISTEN 2570/rpc.statd tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 3046/sendmail: acce tcp 0 0 127.0.0.1:2207 0.0.0.0:* LISTEN 2964/python tcp 0 888 192.168.1.178:22 192.168.1.6:65179 ESTABLISHED 21508/0 tcp 0 0 192.168.1.178:22 192.168.1.6:64535 ESTABLISHED 21187/1 tcp 0 0 192.168.1.178:44496 192.168.1.163:1521 ESTABLISHED 21482/sqlplus
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