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对DBA或需使用exp,imp的普通用戶來说，在我们做exp的過程中可能经常会遇到EXP－00091 Exporting questionable statistics.这样的EXP信息，其实它就是exp的error message，它产生的原因是因为我们exp工具所在的环境变量中的NLS_LANG与DB中的NLS_CHARACTERSET不一致。
问题：
lpding-> exp scott/scott file=/oracle/exp/scott_emp.dmp log scott_emp.log tables=emp
Export: Release 10.2.0.1.0 - Production on Tue Jun 29 15:07:38 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
Export done in UTF8 character set and AL16UTF16 NCHAR character set
server uses ZHS16GBK character set (possible charset conversion)
About to export specified tables via Conventional Path ...
. . exporting table EMP 14 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
Export terminated successfully with warnings.
解决：
SQL> select * from v$nls_parameters where parameter='NLS_CHARACTERSET';
PARAMETER VALUE
------------------------------- ---------------------------------------------------------------------------------------------------
NLS_CHARACTERSET ZHS16GBK
SQL> host
$ export NLS_LANG=AMERICAN_AMERICA.ZHS16GBK
$ exp scott/scott file=/oracle/exp/scott_emp.dmp log scott_emp.log tables=emp
Export: Release 10.2.0.1.0 - Production on Tue Jun 29 15:32:08 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
Export done in ZHS16GBK character set and AL16UTF16 NCHAR character set
About to export specified tables via Conventional Path ...
. . exporting table EMP 14 rows exported
Export terminated successfully without warnings.
lpding->
