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Oracle Redo log cycle in archive log mode

1) The redo logs are spread over disks 1 and 2. The archive log destination is disk 3. Right now, Oracle is writing to redo log group 1.

2) A log switch has occurred, and Oracle is now writing to redo log group 2.

3) At some point after the log switch, Oracle will copy one of the group 1 members to the archive log destination.

4) Now Oracle has advanced to redo log group 3, and group 2 is available to be archived.

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5) Oracle fills group 3, and rolls back around to group 1. The archiver has fallen a bit behind. Group 2 has not been archived yet.

6) Oracle fills group 1, but cannot advance to group2 because it has not been archived yet. This is not good, because now Oracle has to wait.

7) Finally, the archiver catches up a bit and group2 is archived.

8) Oracle is now free to overwrite redo log group 2, so the log switch can occur. The process continues ad infinitum.