在使用EXP工具进行导出备份或迁移数据的时候有时会报很多的“EXP-00091: Exporting questionable statistics”错误，具体的现象和处理方法请观看……

1.问题现象
[oracle@RH207 exp]$ exp test/test file=test.dmf log=test.log
……忽略……
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
. . exporting table                        SNP_TXT       6345 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
. . exporting table                 SNP_TXT_CROSSR       1019 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
EXP-00008: ORACLE error 1013 encountered
ORA-01013: user requested cancel of current operation
EXP-00056: ORACLE error 1403 encountered
……忽略……

2.处理方法
指定Linux系统的NLS_LANG环境变量为数据库的数据集
1）查询数据库的字符集（方法很多只用一种）
SQL> select userenv('language') from dual;

USERENV('LANGUAGE')
----------------------------------------------------
AMERICAN_AMERICA.WE8ISO8859P1

2）设置Linux操作系统的NLS_LANG环境变量
[oracle@RH207 exp]$export NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1

Window系统的环境变量的修改方法是：
C:\>set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1

3.OK，处理完成，在进行EXP导出操作就不会报这个错误了