[Solved] exp:EXP-00091 Exporting questionable statistics

For DBA or ordinary users who need to use exp,imp, we may often encounter EXP-00091 Exporting questionable statistics in the process of doing exp. The reason is that the NLS_LANG in the environment variable where our exp tool is located is not consistent with the NLS_CHARACTERSET in DB. But it should be noted that the error EXP-00091 has no effect on the generated dump file, and the generated dump file can still imp normally.

Let’s solve this problem so that it does not occur again.

Step 1.

Check the value of NLS_CHARACTERSET in DB (two methods are provided).

Query the value of NLS_CHARACTERSET

select * from nls_database_parameters t where t.parameter=’NLS_CHARACTERSET’
select * from v$nls_parameterswhere parameter=’NLS_CHARACTERSET’;

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

———————–  ———————————————-

Step 2.

Set the environment variable for exp based on the NLS_CHARACTERSET (ZHT16BIG5) found in the first step.


set NLS_LANG=AMERICAN_AMERICA.ZHT16BIG5 –windows environment


After setting, check the value of NLS_LANG in the environment variable to see if it is the same, if not, you can change it manually in the environment variable.


export NLS_LANG=AMERICAN_AMERICA.ZHT16BIG5 –linux environment

LINUX> exp export statement


Attached is the oracle error message for exp-00091 Solution Description.

error 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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