解決EXP-00091的方法

最近在做exp的過程中經常會碰見EXP-00091 Exporting questionable statistics的錯誤. 確切的說是個警告，那麼他產生的原因主要就是我們系統環境變數中的NLS_LANG和資料庫中的NLS_CHARACTERSET設定不一致造成的。但是EXP-00091這個對我們所生成的dump影響不大，可以正常的做imp，但是對於有技術強迫症的自己仍然希望他能消失。

解決這個方法還是分兩步走。
step 01　檢視資料庫中的NLS_CHARACTERSET的值

select * from nls_database_parameters t where t.parameter='NLS_CHARACTERSET'

or

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

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

PARAMETER　　　　      VALUE
-----------------------　　----------------------------------------------
NLS_CHARACTERSET    WE8ISO8859P1

step 02　根據我們在step 01查出的NLS_CHARACTERSET(WE8ISO8859P1)，來設定作業系統的環境變數:NLS_LANG

$ export NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1

這個時候我們在exp的時候就不會再出現EXP-00091這個錯誤了

附上exp-91的oracle error message：

oerr exp 91
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.

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