EXP-00091: Exporting questionable statistics

The following warning message is coming while taking the table backup with the EXP utility:

EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.

C:\>exp hr/hr@xepdb1 file=C:\d\hr.dmp log=c:\d\hr.log tables=employees rows=y

Export: Release 21.0.0.0.0 - Production on Fri Apr 14 15:19:27 2023
Version 21.3.0.0.0

Copyright (c) 1982, 2021, Oracle and/or its affiliates.  All rights reserved.


Connected to: Oracle Database 21c Express Edition Release 21.0.0.0.0 - Production
Version 21.3.0.0.0
Export done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set
server uses AL32UTF8 character set (possible charset conversion)

About to export specified tables via Conventional Path ...
. . exporting table                      EMPLOYEES        107 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.
Export terminated successfully with warnings.

Cause: To avoid this we have to use the STATISTICS parameter to None. The default value of this parameter is always.

• ALWAYS : Always import database optimizer statistics regardless of whether they are questionable.
• NONE: Do not import or recalculate the database optimizer statistics.
• SAFE: Import database optimizer statistics only if they are not questionable. If they are questionable, then recalculate the optimizer statistics.
• RECALCULATE: Do not import the database optimizer statistics. It will generate a script with Analyze statement that recalculates at import time.

Solution: Use parameter STATISTICS to None/Safe as follows:

C:\>exp hr/hr@xepdb1 file=C:\d\hr.dmp log=c:\d\hr.log tables=employees statistics=NONE

Export: Release 21.0.0.0.0 - Production on Fri Apr 14 15:22:20 2023
Version 21.3.0.0.0

Copyright (c) 1982, 2021, Oracle and/or its affiliates.  All rights reserved.


Connected to: Oracle Database 21c Express Edition Release 21.0.0.0.0 - Production
Version 21.3.0.0.0
Export done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set
server uses AL32UTF8 character set (possible charset conversion)

About to export specified tables via Conventional Path ...
. . exporting table                      EMPLOYEES        107 rows exported
Export terminated successfully without warnings.