This technical deep-dive covers the architecture, causes, diagnostics, and step-by-step solutions to resolve this error. Understanding the Error Context
Understanding and Fixing ORA-39126: Worker Unexpected Fatal Error in KUPW$WORKER.PREPARE_DATA_IMP [71]
[IMPDP Client] │ ▼ [Master Process (DM00)] ────► Coordinates the job │ ▼ [Worker Process (DW00)] ────► Executes PREPARE_DATA_IMP [71] ──► [CRASH]
impdp ... transform=disable_archive_logging:y transform=constraints:n transform=indexes:n This is an internal error"
According to Oracle’s official documentation, ORA-39126 signifies that "An unhandled exception was detected internally within the worker process for the Data Pump job. This is an internal error". In essence, a slave process responsible for performing a subtask (unloading, transforming, or loading data) encountered an unexpected exception that the system’s internal exception handlers could not recover from.
If Data Pump continues to fail, export using legacy exp and import with imp (may lose advanced features but works for many data-only scenarios).
This error typically halts an import job, often leaving behind a log file with minimal actionable clues. This comprehensive guide breaks down the anatomy of this error, explores its root causes, and provides a multi-level, step-by-step roadmap for diagnosing and resolving the issue. This error typically halts an import job, often
impdp ... ACCESS_METHOD=EXTERNAL_TABLE
When the error is linked to a specific object type, the quickest workaround can be to exclude it from the operation. This is particularly effective for objects like table statistics ( EXCLUDE=STATISTICS ) or problematic Advanced Queuing (AQ) tables. While you may lose some data in the process, you can often recreate or re-import it later, allowing the main job to succeed.
ALTER SYSTEM SET "_disable_asynch_sampling"=TRUE; (Consult with a DBA before changing hidden parameters). Summary Checklist ALTER SYSTEM SET "_disable_asynch_sampling"=TRUE
Corrupt or invalid KUPW$WORKER or DBMS_METADATA package bodies can prevent the worker from initializing correctly.
EXEC DBMS_STATS.GATHER_SCHEMA_STATS('YOUR_SCHEMA_NAME');
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