How to resolve the issue when Oracle’s merge operation does not update data.

When using the MERGE statement in Oracle for data updates, if the update operation does not take effect, it may be due to a few reasons:

1. Conditions not met: The ON condition in the MERGE statement and the conditions in the WHEN MATCHED/WHEN NOT MATCHED clauses may not correctly match the data to be updated. Please ensure the conditions are correct and check if the data meets the conditions.
2. Concurrency conflict: If other sessions are simultaneously modifying the data to be updated, it may result in the MERGE statement failing to update the data successfully. In such cases, you can try using the FOR UPDATE clause to lock the data to be updated, or utilize row-level locking features.
3. Issue: If a rollback or commit operation occurs during the execution of the MERGE statement, it may result in data not being updated. Make sure the MERGE statement is executed in a complete transaction and check the isolation level of the transaction.
4. Permission issue: If the user does not have sufficient permissions for the table to be updated, they may not be able to update the data. Please ensure that the user has the appropriate update permissions.

If the above methods do not solve the problem, you can use SELECT statements before and after the MERGE statement to validate whether the correct data is being retrieved for updating and if the data is being modified correctly after the update. If the issue still cannot be resolved, further inspection of the database and table configurations may be necessary, or contacting the Oracle support team for troubleshooting.