In an earlier post, we saw how Oracle’s UNDO works in very basic terms. REDO is another critical aspect that goes hand in hand with UNDO. Let us get the basics of REDO sorted out here. UNDO and REDO In its most basic sense UNDO is information saved to get back in case a ROLLBACK … Continue reading Oracle REDO – A Basic Explanation
Why is the APPEND hint so great? In a prior post, we extolled the virtues of the APPEND hint (AKA Direct Path Insert). It is a great option to use • UNDO usage is negligible. It is only generated for index maintenance and meta data changes. The keyword is index maintenance – indexes generate UNDO. … Continue reading Oracle – Is my APPEND Hint Being Ignored? How To Find Out?
The v$session view If you do not know already, to check who is connected and since when, what their connection status is etc., you would use dynamic view v$session. The view has the following columns: You would kill the required session by issuing Note: The IMMEDIATE option of the above command just returns control … Continue reading Oracle – My KILL’ed Session Continues To Stay On In KILLED Status, Why?
Why DELETE is bad? In Oracle, when it comes to deleting ** A L L ** the data from a table (clearing the contents of a staging table for example), using a DELETE statement is the most inefficient choice. Here are some reasons why DELETE is bad It uses UNDO It uses REDO It fires … Continue reading Oracle – TRUNCATE vs DELETE – Spoiler: TRUNCATE Wins & Why? Hours vs Seconds!
You might have heard the terms UNDO and REDO thrown around in conversations around space usage. In this tip, let us get a basic idea of what UNDO (formerly called ROLLBACK) is in Oracle. I promise you that this will be an interesting read and you will be happy you read this. Unlike SQL Server … Continue reading Oracle UNDO – A Basic Explanation