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What happens to redo information when DB not in Archivelog mode?

Jose Manuel
Jose Manuel Member Posts: 2 Green Ribbon
edited May 11, 2021 4:27PM in Database Security - General

Hello there,

I'd like to know what happens if your DB is not running on Archivelog mode? We know LGWR process copies redo information from its buffer into the redo log files, but the ARCH is the one who copies the info from redo log files into the disk.

Does this mean that if for example I have 3 redo log files and they're all full, I wouldn't be able to save more redo log information?

And if for example, this 3 full-redo log contain information from the last week but my DB crashes and I need to recover the last 2 weeks info, could I only recover the last week info or everything would be lost since it wouldn't be written on a disk?

Thanks and greetings


Best Answer

  • EdStevens
    EdStevens Member Posts: 28,778 Gold Crown
    Answer ✓

    If you are not in archivelog mode, then the redo logs are continually overwritten, losing the information.

    Redo log 1 fills up, so logwr starts writing to redo log 2.

    Redo log 2 fills up, so logwr starts writing to redo log 3.

    Redo log 3 fills up, so logwr starts writing to redo log 1, over writing what was the from earlier .....

    If you are in NOarchivelog mode, the only 'recovery' that will be possible is instance recovery.

    Jose ManuelBlaise NOUTCHEU