（一）参数说明：
（1）. rate_limit参数从9.2.0.8引入，可以用来控制连接风暴。rate_limit后面跟的参数是允许每秒连接的个数，配置完成后，需要stop/start listener生效。如下：

LISTENER = 
  (DESCRIPTION_LIST = 
    (DESCRIPTION = 
      (ADDRESS = (PROTOCOL = TCP)(HOST = host.sample.com)(PORT = 1521)(RATE_LIMIT=5)) 
    ) 
    (DESCRIPTION = 
      (ADDRESS = (PROTOCOL = TCP)(HOST = host.sample.com)(PORT = 1522)) 
    ) 
   )

上面的配置表示1521端口只允许每秒5个连接，而1522端口是没有限制的。

配置以后，在listener.log中，如果有超过设置的连接数，会报错tns-1158：
在11：42：24这个时刻，可以看到最多5个连接，超出的就报错tns-1158了。

15-MAY-2010 11:42:24 * establish * 1158

TNS-01158: Internal connection limit reached, preventing dispatcher from connecting

15-MAY-2010 11:42:24 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60340)) * establish * S111W6 * 0

15-MAY-2010 11:42:24 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60341)) * establish * S111W6 * 0

15-MAY-2010 11:42:24 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60342)) * establish * S111W6 * 0

15-MAY-2010 11:42:24 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60344)) * establish * S111W6 * 0

15-MAY-2010 11:42:24 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60343)) * establish * S111W6 * 0

15-MAY-2010 11:42:25 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60345)) * establish * S111W6 * 0

15-MAY-2010 11:42:25 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60346)) * establish * S111W6 * 0

15-MAY-2010 11:42:25 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60347)) * establish * S111W6 * 0

15-MAY-2010 11:42:25 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60349)) * establish * S111W6 * 0

15-MAY-2010 11:42:25 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=S111W6)(CID=(PROGRAM=sqlplus)(HOST=sample.com)(USER=grdbms))) * (ADDRESS=(PROTOCOL=tcp)(HOST=sample.com)(PORT=60348)) * establish * S111W6 * 0

（2）. 除了上面的这种配置，还有另外一种配置方式，设置connection_rate_listener

LISTENER = 
  (DESCRIPTION_LIST = 
    (DESCRIPTION = 
      (ADDRESS = (PROTOCOL = TCP)(HOST = host.sample.com)(PORT = 1521)(RATE_LIMIT=YES)) 
    ) 
    (DESCRIPTION = 
      (ADDRESS = (PROTOCOL = TCP)(HOST = host.sample.com)(PORT = 1522)(RATE_LIMIT=YES))
    ) 
  ) 
CONNECTION_RATE_LISTENER=10

上述配置表示1521和1522端口，都受到rate_limit的限制，每秒最多连接数是10个。

（二）已知问题
（1）. Bug 8529537 : ALL NEW CONNECTIONS ARE REFUSED BY ORA-12547 AFTER TNS-01158 IN LISTENER.LOG
描述：当达到设置rate_limit的最大值之后，报错tns-1158，但是后续新的连接无法连接了。
受影响版本：11.2.0.1、11.1.0.7、10.2.0.4
Fix版本：11.2.0.2 、 12.1

（2）. Bug 16409926：LISTENER MEMORY LEAK IF RATE_LIMIT IS USED AND ENFORCED FREQUENTLY
描述：设置rate_limit之后，过来的连接需要花费较长的时间才能建立，tnsping的响应也需要较长时间，重启listener之后可以解决问题，但是不久之后问题重现。
受影响版本：11.2
Fix版本：11.2.0.4 and 12.1.0.2，或者应用patch 16409926。

（三）相关文档：
How To Control the Amount of Connections Handled by the TNS Listener (Doc ID 443744.1)
TNS Listener Hang Every 49.X Days (Doc ID 1357676.1)
11gR2 Listener With RATE_LIMIT Set: Slow Connect Time and Tnsping Response Time High with TNS-1158 Error (Doc ID 1568591.1)
ORA-12547 & TNS-01158: Listener Stops Allowing Connections When Rate_Limit Feature is in Place (Doc ID 1085546.1)