Hi Perry,
First, thanks a lot for your article. I find it very helpful.
In the level 6, Dialog box in diagram 6.30 mentions "startup of database". Do you mean startup of 'instance' ?
The database is a collection of files, we do not start a database. Meanwhile, an instance is a background-process; we start a background-process.
The in level 7, diagram 7.1 and 7.2 contain 'AONODE'. Are they (the nodes with prefix AONODE) separately created? The previous levels have no example creating them.
Thanks