EXP-00091: Exporting questionable statistics.

EXP-00091正在导出有问题的统计信息

EXP-00091: Exporting questionable statistics.

Cause: Export was able export statistics, butthe statistics may not be usuable. The statistics are questionable because one or more of the following happened during export:a row error occurred, client character set or NCHARSET does not match with the server, a query clause was specified on export, only certain partitions or subpartitions were exported, or a fatal error occurred while processing a table.

Action: To export non-questionable statistics, change the client character set or NCHARSET to match the server,export with no query clause, export complete tables. If desired, import parameters can be supplied so that only non-questionable statistics will be imported, and all questionable statistics will be recalculated.

解决方案：

依照官方文档的说明，是可能由于数据库行有错误、客户端字符集与数据库字符集不匹配、exp语句定义了query选项（表的部分导出、分区导出）、或者是致命错误导致的表统计信息不全，从而触发exp-00091。

那么，首先设定客户端与数据库服务器字符集匹配。

1、查看数据库端服务器字符集。

       select userenv('language') from dual;

2、设定服务器字符集为数据库字符集。

       export NLS_LANG=

3、若是windows服务器，添加NLS_LANG系统环境变量即可。

更详细内容参考：

http://blog.csdn.net/dracotianlong/article/details/8270363

4、如果是表中定义了query选项，那么To export non-questionable statistics（导出表数据时候，不导出统计信息）

  exp userid=xcky/xcky file=./xcky`date +%y%m%d`.dmp tables=emptb query=\"where rownum \< '100'\"

    statistics=none buffer=720000 log=./xcky`date +%y%m%d`.log

5、如果以上操作后，依旧报exp-00091错误，考虑是由于row error或fatal error occurred.