In Oracle databases, NOLOGGING is often used to minimize redo log generation for certain operations. However, many users wonder why DELETE cannot be NOLOGGING and how to efficiently remove large volumes of data without impacting performance.

Why DELETE Always Generates Redo and Undo Logs

The DELETE statement in Oracle generates redo and undo logs for the following reasons:

1. Data Integrity & Rollback Support
   • Oracle must track changes to allow transactions to be rolled back if needed.
   • Undo logs store the original values of deleted rows.
2. Redo Logs for Crash Recovery
   • Redo logs ensure that deleted data is permanently removed, even if the system crashes mid-operation.
3. Row-by-Row Processing
   • Unlike TRUNCATE, which operates at the segment level, DELETE works row-by-row, making logging necessary.

How to Efficiently Delete Large Data Volumes

1. Use TRUNCATE Instead of DELETE (If Possible)

If you need to remove all rows from a table without undo logging, use TRUNCATE

TRUNCATE TABLE table_name;

✅ Pros: Fast, minimal redo/undo logging

❌ Cons: Cannot be rolled back, does not trigger ON DELETE triggers