今天客户的一批新测试数据被加载到试运行环境的数据库(OEL5.7，ORACLE11gR2)，项目经理要求这批数据导入完成后将数据库做个备份，在用EXP做备份的时候，出现了EXP-00091错误，如下：

Export:Release 11.2.0.2.0-Production on Tue Feb 28 16:16:23 2012
Copyright(c)1982,2009,Oracle and/or its affiliates.
Connected to: Oracle Database 11g Enterprise Edition Release
11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application T
esting options
Export done in US7ASCII character set and AL16UTF16 NCHAR
character set server uses AL32UTF8 character set (possible
charset conversion)
About to export specified users ...
. exporting pre-schema procedural objects and actions
. exporting foreign function library names for user DIGITAL
. exporting PUBLIC type synonyms
. exporting private type synonyms
. exporting object type definitions for user DIGITAL
About to export DIGITAL's objects ...
. exporting database links
. exporting sequence numbers
. exporting cluster definitions
. about to export DIGITAL's tables via Conventional Path ...
. . exporting table            GUANWAINIAN      10218 rows exported
EXP-00091: Exporting questionable statistics.
. . exporting table                  IMAGE          0 rows exported
EXP-00091: Exporting questionable statistics.
. . exporting table      T_BATCH_CHECK_COL         14 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
. . exporting table       T_BATCH_COLUMN_R       1239 rows exported
EXP-00091: Exporting questionable statistics.
. . exporting table    T_BATCH_EXPORT_INFO         20 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
. . exporting table      T_BATCH_FILE_INFO         42 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
. . exporting table           T_BATCH_INFO         45 rows exported

ORACLE提示操作系统使用US7ASCII字库，而数据库是AL32UTF8字符集，需要转换，查看数据库字符集：

SQL> select * from v$nls_parameters where parameter='NLS_CHARACTERSET';

PARAMETER           VALUE
----------------   --------
NLS_CHARACTERSET   AL32UTF8

查看操作系统用户ORACLE的NLS_LANG变量：

[oracle@fhacdb ~]$ env | grep NLS_LANG
[oracle@fhacdb ~]$ echo $NLS_LANG

以上命令都没有结果返回，NLS_LANG变量没有设置，默认使用US7ASCII字库，修改NLS_LANG变量和数据库的字符集一致。

[oracle@fhacdb ~]$ export NLS_LANG=AMERICAN_AMERICA.AL32UTF8

再次使用EXP导出数据，问题解决。

Export: Release 11.2.0.2.0 - Production on Tue Feb 28 16:33:20
Copyright (c) 1982, 2009, Oracle and/or its affiliates.
All rights reserved.
Connected to: Oracle Database 11g Enterprise Edition Release
11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application
Testing options
Export done in AL32UTF8 character set and AL16UTF16 NCHAR
character set
About to export specified users ...
. exporting pre-schema procedural objects and actions
. exporting foreign function library names for user DIGITAL
. exporting PUBLIC type synonyms
. exporting private type synonyms
. exporting object type definitions for user DIGITAL
About to export DIGITAL's objects ...
. exporting database links
. exporting sequence numbers
. exporting cluster definitions
. about to export DIGITAL's tables via Conventional Path ...
. . exporting table            GUANWAINIAN      10218 rows exported
. . exporting table                  IMAGE          0 rows exported
. . exporting table      T_BATCH_CHECK_COL         14 rows exported
. . exporting table       T_BATCH_COLUMN_R       1239 rows exported
. . exporting table    T_BATCH_EXPORT_INFO         20 rows exported
. . exporting table      T_BATCH_FILE_INFO         42 rows exported
. . exporting table           T_BATCH_INFO         45 rows exported
. . exporting table  T_BATCH_INFO_AUTOCHECK         0 rows exported
. . exporting table        T_BATCH_QUALITY        336 rows exported
. . exporting table     T_BATCH_STATISTICS         41 rows exported
. . exporting table           T_DICTIONARY     123371 rows exported
......

在EXP报错的时候，ORACLE已经提示客户端的字库和数据库的字符集不一致，需要转换。

Export done in US7ASCII character set and AL16UTF16 NCHAR
character setserver uses AL32UTF8 character set
(possible charset conversion)
About to export specified users ...

而设置NLS_LANG和数据库的字符集一致后，由于字符集已经一致，ORACLE就不需要再提示。

Export done in AL32UTF8 character set and AL16UTF16 NCHAR
character set About to export specified users ...

遇到问题时不要慌张，ORACLE的很多错误都会有详细的提示，一般只要细心观察，都会找到解决问题的方法。

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