Re: What to do with archived redo-logs ?

A little background might help:
Redo logs record all of the changes to the user objects or system objects in a database. When one of them fills up the database switches to the other one. And it fills that one up. (Oracle databases have a minimum of 2 redo logs). Oracle keeps using as many new redo log files as it has available, then it cycles back to the old ones. Depending on the activity in the database you could switch redo logs files once every xx minutes or once every day.

Running in archive log mode means that after one of these logs fills up, the database will copy it to another directory where it's safe and won't be reused. However, we all know that the problem is how to manage these "offline" redo logs or Archived redo logs. They tend to eat up disk space. So you keep some on disk and backup the others to tape and delete them.

When a database becomes corrupt you want / need to recover it to the most current point and time possible. You'll need all of the archive logs to do that. If you're missing one in the middle you have to recover to before the time it used that archive log file. If you're missing the most current ones you have to recover to before that time. So, Yes, you need them all. And we were getting 2 tape copies of all archive logs (keeping 2 old days + the current day on disk) and backing them up each night. We felt that protected us from a bad tape or anything else going wrong. We wanted to keep 3 days worth on line but we didn't want to use that much disk space and we admited that might be a little too overprotective.

Running in archive log mode is for 2 reasons: it allows you to do online backups which means that you can keep the database up and going during the backup (important for 24x7 shops) and it allows you to recover to the most current time possbile . Otherwise you shut down your database, do a "cold" backup and you can only recover to the last good "cold" or offline backup.

this is probably more than you wanted to know! hope it helps a little.

Stephanie Received on Sun Jan 04 1998 - 00:00:00 CST