怎么确保最终用户在数据库中只有一个会话

sqlplus / as sysdba
create user test identified by test;
create profile one_session limit sessions_per_user 1;
alter user test profile one_session;
alter system set resource_limit=true;
conn test/test
host sqlplus test/test

SQL*Plus: Release 10.2.0.3.0 - Production on 星期二 8月 11 17:09:05 2009

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ERROR:
ORA-02391: 超出同时存在的 SESSIONS_PER_USER 限制