Explanation:
Any user performing an entire export and import must have the EXP_FULL_DATABASE and IMP_FULL_DATABASE roles, respectively. By default the IMP_FULL_DATABASE is assigned to the DBA. Granting the DBA role thereby enables the user to import the full database from an export dump file.
Reference:
Oracle 9i Net Services Administrator’s Guide
Oracle 9i Net Services Reference Guide
Oracle 9i Recovery Manager Reference
Oracle 9i Backup and Recovery Concepts

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