ORA-12545: Connect failed because target host or object does not exist

[oracle@ybdbtest oradata]$ sqlplus /nolog


SQL*Plus: Release 9.2.0.4.0 - Production on Thu Jun 26 10:16:29 2014


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SQL> conn / as sysdba

ERROR:
ORA-12545: Connect failed because target host or object does not exist

记得昨天都连上去了，怎么回事，查看oracle进程，进程存在，说明数据库是运行的。

[oracle@ybdbtest ~]$ ps -ef | grep ora_
oracle    5013  4499  0 11:33 pts/1    00:00:00 grep ora_
oracle   11806     1  0  2013 ?        00:00:00 ora_q001_szyb
oracle   12212     1  0  2013 ?        00:08:51 ora_pmon_szyb
oracle   12214     1  0  2013 ?        00:00:02 ora_psp0_szyb
oracle   12216     1  0  2013 ?        00:00:00 ora_mman_sz