Ora-39126 Worker Unexpected Fatal Error In Kupw-worker.prepare-data-imp 71 -

The ORA-39126 error in KUPW$WORKER.PREPARE_DATA_IMP [71] indicates an internal Data Pump failure during import, often caused by corrupted Data Pump catalogs, PDB/CDB mismatches, or issues within the temporary tablespace. Resolving the issue typically involves validating the Data Pump catalog, ensuring the temporary tablespace is valid, or using the EXCLUDE=STATISTICS parameter. For a detailed troubleshooting guide, refer to Oracle Communities

ORA-39126: Worker unexpected fatal error in KUPW$WORKER.PREPARE_DATA_IMP [71] — oracle-mosc

A very specific Oracle error!

ORA-39126 is a Data Pump error that occurs when there is an issue with the worker process. Here's a breakdown of the error:

ORA-39126: Worker unexpected fatal error in KUPW_WORKER.PREPARE_DATA_IMP

This error typically indicates that a worker process, which is responsible for executing a specific task during the import operation, encountered an unexpected fatal error while preparing data for import.

Possible causes:

Data corruption: Data corruption during the export or import process can cause this error.
Insufficient resources: Inadequate resources, such as memory or CPU, can lead to worker process failures.
Data Pump version mismatch: A mismatch between the Data Pump versions used for export and import can cause compatibility issues.
Database character set issues: Character set mismatches or invalid characters in the data can cause errors during import.
Internal errors: Rarely, internal errors in the Data Pump code can cause this error.

Additional information:

The error is occurring in the KUPW_WORKER.PREPARE_DATA_IMP procedure, which is part of the Data Pump worker process. The error code is 71, which is an internal Oracle error code.

Troubleshooting steps:

Check the import log: Review the import log file for any previous errors or warnings that may have contributed to this error.
Verify data integrity: Check the data for corruption or inconsistencies.
Increase resources: Ensure that the system has sufficient resources (e.g., memory, CPU) to perform the import.
Check Data Pump versions: Verify that the Data Pump versions used for export and import are compatible.
Try a different import method: If possible, try using a different import method, such as a conventional import or a transportable tablespace import.

Oracle Support or further assistance:

If you are unable to resolve the issue using the above steps, you may want to engage Oracle Support or a certified Oracle professional for further assistance. They can help you:

Analyze the import log and error files
Check for any known issues or patches related to this error
Perform additional troubleshooting steps
Provide guidance on recovering the import process, if possible.

The Investigation

The log file was messy. The error was followed by a cascade of Java stack traces, looking like digital debris after a car crash. He scrolled past the ORA-39126 to find the root cause buried beneath it. The ORA-39126 error in KUPW$WORKER

ORA-01653: unable to extend table SYSTEM.SYS_EXPORT_TABLE_01 by 1024 in tablespace USERS

Arthur let out a breath he didn’t know he was holding. It wasn’t corruption. It wasn't a hardware failure. The worker process—KUPW$WORKER—had tried to prepare a chunk of data for import, hit a wall, and threw its hands up in a "fatal error."

The Data Pump worker process had essentially walked into a room that was already full. The tablespace where the temporary import tables were being built had run out of space. Because it couldn't write the data it was preparing, the worker process crashed, triggering the generic ORA-39126 alert.

Step 8: Recreate the Dump File

If all else fails, return to the export step:

Ensure FILESIZE limits are not creating multiple fragments
Use COMPRESSION=ALL to reduce corruption risks
Transfer using rsync or binary FTP
Validate checksums (DBMS_DATAPUMP.GET_DUMP_FILE_INFO)

7. Workaround – Use legacy Import

If Data Pump consistently fails, try the original imp utility (if export was done with original exp).

Diagnostic Methodology

Resolving ORA-39126 requires moving beyond a simple retry. The DBA must adopt a forensic approach: Data corruption : Data corruption during the export

Examine the Complete Log: The error message typically includes a secondary exception. Using impdp ... LOGFILE=detailed.log may reveal a ORA-31623, ORA-39125, or ORA-01403 immediately preceding the fatal error. This secondary error is the key to the root cause.
Identify the Culprit Table: The Data Pump log often names the table being imported when the error occurred. Isolating this table is critical.
Test with SQLFILE Parameter: Run the import with impdp ... SQLFILE=ddl.sql. This generates the DDL without executing it. If the DDL fails to generate or contains anomalies, the metadata is corrupted.
Check Versions: Compare the source and target database versions and patch levels. Mismatched versions (especially across major releases like 12.1 to 12.2) are common triggers.

The Night the Data Pipeline Broke

The clock on the wall read 2:14 AM. Outside the server room, the city was asleep, but inside, the air conditioning hummed a monotonous drone. Arthur, the lead DBA, was running the final migration script for the company’s new CRM system. The stakeholder meeting was at 8:00 AM, and the data pump import job was at 94%.

"Almost there," Arthur whispered, watching the terminal scroll with satisfying speed. Rows were being processed, indexes were building. He reached for his cold coffee, ready to celebrate a smooth deployment.

Then, the scrolling stopped.

It didn’t stop with a gentle "Job completed" message. It stopped with a violent, jagged block of text that turned his stomach into a knot.

ORA-39126: Worker unexpected fatal error in KUPW$WORKER.PREPARE_DATA_IMP

Arthur froze. The error code ORA-39126 was generic, a catch-all for "something terrible happened inside a Data Pump worker process." The specific location—KUPW$WORKER.PREPARE_DATA_IMP—told him the failure happened during the data preparation phase. The job wasn't just paused; it was dead. Additional information: The error is occurring in the

He scrambled to check the log file, his fingers shaking slightly over the keyboard.