在EXP导出时，出现EXP-00091报错：

. . exporting table                         FRIEND
..............
                                                       142480 rows exported
EXP-00091: Exporting questionable statistics.

查看EXP-00091的oracle error message 解决方案说明：

[oracle@MWSG1: ~]$oerr exp 00091
00091, 00000, "Exporting questionable statistics."
// *Cause:  Export was able export statistics, but the 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.

    在我们做exp的过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。

⑴ 我们来查看DB中的NLS_CHARACTERSET的值（提供两种方法）：

sys@CCDB> select * from nls_database_parameters t where t.parameter='NLS_CHARACTERSET'; PARAMETER                VALUE ------------------------- --------------- NLS_CHARACTERSET          AL32UTF8 或者 sys@CCDB> select * from v$nls_parameters  where parameter='NLS_CHARACTERSET'; PARAMETER                VALUE ------------------------- --------------- NLS_CHARACTERSET          AL32UTF8

⑵ 查看环境变量中的NLS_LANG：

[oracle@MWSG1: ~]$echo $NLS_LANG
AMERICAN_AMERICA.ZHS16CGB231280      --果然与DB中NLS_CHARACTERSET＝AL32UTF8不同。

⑶ 根据⑴查出的NLS_CHARACTERSET（AL32UTF8）来设定exp的环境变量：

WINNT> set NLS_LANG=AMERICAN_AMERICA.AL32UTF8
[oracle@MWSG1: ~]$export NLS_LANG=AMERICAN_AMERICA.AL32UTF8
[oracle@MWSG1: ~]$echo $NLS_LANG
AMERICAN_AMERICA.AL32UTF8       --设置与DB中NLS_CHARACTERSET＝AL32UTF8相同。

⑷ 再来EXP导出数据 查看log中是否还有EXP-00091报错？   

. . exporting table                         FRIEND
...........................................................................
..............................................
                                                      1216253 rows exported
. . exporting table                     FRIEND_GRP
                                                          128 rows exported
Export terminated successfully without warnings.      --成功导出且没警告。

EXP-00091问题解决了！

转自http://blog.chinaunix.net/uid-23072872-id-35007.html