Question

I understand the Database isolation levels which is very well documented in Wikipedia and Oracle documentation.

I have few questions perhaps:

1. For a particular isolation level, does database only decides the resource to lock(e.g. table, row, or data in a column) or this is configurable?
2. Other than Isolation Levels, can a user/application exclusively create lock on some resource? If not, why?

Answer 1

Oracle will automatically handle locks for all isolation levels. Oracle also lets you set locks yourself.

How Oracle locks data