【www.bbyears.com--Oracle教程】
（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。