Rollback Segment vs Redo log

[khoshtip_uk]

Hi guys, I have come across below paragraph today …

“ A Rollback Segment is a database object containing before-images of data written to the database. Rollback segments are used to:
• Undo changes when a transaction is rolled back
• Ensure other transactions do not see uncommitted changes made to the database
• Recover the database to a consistent state in case of failures “
My understanding is that Oracle also stores before image for committed and uncommitted transactions in the redo-log files! So the question is why does Oracle need rollback segment? Why cant Oracle provide rollback functionality/read consistency and recovery by using the redo log files?
Thanks!

[malay_biswal]

For back up recovery Oracle uses Redo logs.

Before data committed you need Undo segments data.
After commit you need Redo log data to recover.

[davey23uk]

Hi guys, I have come across below paragraph today …

“ A Rollback Segment is a database object containing before-images of data written to the database. Rollback segments are used to:
• Undo changes when a transaction is rolled back
• Ensure other transactions do not see uncommitted changes made to the database
• Recover the database to a consistent state in case of failures “
My understanding is that Oracle also stores before image for committed and uncommitted transactions in the redo-log files! So the question is why does Oracle need rollback segment? Why cant Oracle provide rollback functionality/read consistency and recovery by using the redo log files?
Thanks!

that is one of the most basic concepts of oracle - in fact the most important one

go and read the concepts manual

your statement about redo logs is very very wrong