You should definately read the documentation regarding this subject. It is SO large and detailed. There would be no point to describe EVERYTHING that these two things do. Also, Do a "search" on this Forum for archives regarding this information.
Basically, archived logs and redo logs are a KEY ingredient to any Backup&Recovery procedure. In fact, it would be fairly impossible to Recover a database if you did not have any of these logs (backed up or otherwise).
You cannot run a database without redo logs.
Again, read the archives on this subject or Oracle Documentation. There is way too much information out there to go into detail on this broad subject.
To start with the database can be in two modes; archived log mode or noarchived log mode
Archived logs are redologs archived so basically what you need to understand is what are redologs
everything we do in the database is being logged (except queries of course), things like modifying db structure, adding data etc
Letīs assume we are in archived log mode:
For example if I accidently deleted some data and commit the transaction there must be some way I can go back to the moment just befre I deleted the data, one way would be restore a backup from yesterday for example and start giving the archived logs to Oracle so he can read it and do all the changes in the db during the backup until the moment of my bad transaction. Itīs like a diary for Oracle
Thanks a lot. Can you please explain what kind of Trobles can we expect from Redo Logs and How we Handle. Should we Remove the Contents of Redo Logs if we don't need them or Should Increase the Size for Redo Logs or add new members.
Your signature states that you are "certified" in 8i. Am I to assume that you were not educated regarding redo-logs/archived logs?
You should AT LEAST have 2 members per Redo Log and have them located on separate disks. That way, if one of your disks has a problem, you already have a copy (the other member).
You cannot remove contents of redo logs. They exist, and re-write themselves (that's where the archived logs come in). So, you could have three groups of Redo Logs with 2 members each. Once Group 1 is full, Group 2 takes over, etc. Once Group 3 is full, then Group 1 is over-written.