Check for known bugs:

If the error persists, a more systematic approach is necessary. The first step is to examine the Data Pump log file. But for deeper insight, you need to look at the detailed trace files.

Use select count(*) from dba_objects where status = 'INVALID'; . Compile invalid objects using utlrp.sql . 3. Exclude Statistics

Run impdp with LOGFILE and TRACE to see preceding errors:

Compile invalid objects with ALTER ... COMPILE before exporting.

Understanding ORA-39126 During Data Pump Import The is a generic wrapper error in Oracle Data Pump. It indicates that an internal worker process encountered an unhandled exception and failed. When paired with KUPW$WORKER.PREPARE_DATA_IMP [71] , it pinpoints a specific failure location. The worker process crashed while executing internal code block 71 during the data preparation phase of an import ( impdp ) operation.

[IMPDP Client] │ ▼ [Master Process (DM00)] ────► Coordinates the job │ ▼ [Worker Process (DW00)] ────► Executes PREPARE_DATA_IMP [71] ──► [CRASH]

Before implementing a fix, a thorough diagnosis is recommended. Follow this structured approach to gather necessary information:

If moving data across different Oracle releases, explicitly state the database version compatibility. If your target database is 19c and the source was 21c, add the target version to your command line:

When PREPARE_DATA_IMP fails, Data Pump is attempting to analyze the export dump file and map it against the target database's architecture. The failure typically stems from one of four core system anomalies: 1. Version and Compatibility Mismatches

can trigger unexpected behavior or performance issues; it is recommended to use a user with the DATAPUMP_IMP_FULL_DATABASE role instead. Metadata Corruption : The Data Pump packages or required views (like SYS.DBMS_METADATA ) might be invalid or missing. Version Mismatch

: Using a newer export version to import into an older database version without setting the parameter correctly. Resource Issues