1) Normally, Oracle only writes changed data into the redo logs (deltas). When the database is in backup mode, Oracle writes full copies of the blocks to the redo logs, not just changes with the block. As a result, the redo generation increases when the database is in backup mode.
2) When you use RMAN for online backups, the database doesn't have to be put into backup mode, so there is no extra redo generated. This can be massively advantageous for systems that are busy during backups.
3) Hopefully a crash will recover itself, but if not, you need to do something like this.
Code: Select all
alter database open;