Oracle Concepts - Oracle commit Processing

A commit is a very important Oracle concept. As users make changes in Oracle, those changes are only visible to the user session making the change and are unrecoverable in the case of a crash. A commit changes all that. When the user tells Oracle to commit the change, Oracle makes the change visible to everyone, and ensures that the change is recoverable.

Since RAM is wiped out if you lose power to the computer, all the redo data in the redo buffer would be lost in a power outage. To protect against this problem, a commit asks Oracle to save the redo to disk, which is permanent. The redo log disk files are called online redo logs.