The Oracle error ORA-39126: Worker unexpected fatal error in KUPW$WORKER.PREPARE_DATA_IMP [71] is a generic "catch-all" internal error during a Data Pump import (impdp). It typically indicates that a worker process encountered an unhandled exception while preparing data for insertion. Primary Causes
The full error message usually appears as: The Oracle error ORA-39126: Worker unexpected fatal error
PDB Metadata Mismatch: If you are using Oracle 12c or higher, this error often occurs in Pluggable Databases (PDBs) where the Data Pump catalog is invalid or incomplete, frequently after a remote clone. Then, the scrolling stopped
Arthur checked the disk usage. The USERS tablespace was at 99.9% capacity. The migration had simply been too large for the allocated space. the scrolling stopped.
Additional information:
impdp ... PARALLEL=1 # or match CPU cores
impdp ... ACCESS_METHOD=SEQUENTIAL_FILE
Then, the scrolling stopped.