Have you ever had to make fundamental changes to a table in Oracle, but haven't been able to get any downtime? I'm talking things like:
* Dropping columns
* Shrinking allocated space
* Removing chained blocks and restoring the PCTFREE
This post first appeared at Oracleinaction (http://oracleinaction.com/undo-and-redo-in-oracle/)by Anju Garg (Myself).
I will demonstrate that undo for DML’s is stored both in undo tablespace and online redo logs. Then, we will analyze the reaso…