當你要進行EXP/IMP時，而source database 的 nls_language 設定與 target database 的 nls_language不同時, 你在export data 時, 可以先將 nls_lanaguage設定成 target database 的 nls_lanaguage, 如此可避免字元集不相容的情形發生
Export and Character Set Conversion
Conventional path export writes export files using the character set specified for the
user session, for example, 7-bit ASCII or IBM CODE Page 500 (EBCDIC).
Direct path export exports in the database character set only. If the character set of the
export session is not the same as the database character set when an export is initiated,
Export displays a warning and aborts. Specify the session character set to be the same
as that of the database before retrying the export.
The export file contains a flag that shows the character encoding scheme used for its
character data.
Import and Character Set Conversion
The import session and the target database character set can differ from the source
database character set. This situation requires one or more character set conversion
operations.
If necessary, the export file data is first converted during import to the character
encoding scheme specified for the user session, and then to the database character set.
During the conversion, any characters in the export file that have no equivalent in the
target character set are replaced with a default character, which is defined by the target
character set. To guarantee 100% conversion, the target character set must be a
superset of or equivalent to the source character set.
Guidelines
Because character set conversion lengthens the processing time required for import,
limit the number of character set conversions to as few as possible. In the ideal
scenario, the import session and target database character sets are the same as the
source database character sets, requiring no conversion.
Note: The setting of the character set at the session level and its impact on various
database operations are covered in detail in the lesson “Using National Language
Support.”
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