今天用EXP命令导Oracle数据库，出现如下错误信息：

[oracle@yingxiang-testServer1 ~]$ exp imgpf/imgpf@orcl file=/prlife/db/USDMP20140428.dmp

Export: Release 11.2.0.4.0 - Production on Mon Apr 28 09:53:47 2014

Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.

EXP-00056: ORACLE error 12154 encountered
ORA-12154: TNS:could not resolve the connect identifier specified
EXP-00000: Export terminated unsuccessfully

查看$ORACLE_HOME/network/admin下的 tnsnames.ora 文件，如下所示：

ORCL_YZJ =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.132.2.147)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = orcl)
)
)

于是，执行导出表命令如下，导出成功：

[oracle@yingxiang-testServer1 ~]$ exp imgpf/imgpf@ORCL_YZJ file=/home/oracle/table_space/USDMP20140428.dmp

Export: Release 11.2.0.4.0 - Production on Mon Apr 28 14:54:58 2014

Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Export done in UTF8 character set and UTF8 NCHAR character set
server uses AL32UTF8 character set (possible charset conversion)

About to export specified users ...
. exporting pre-schema procedural objects and actions