The following steps are performed when a user requests for some information:
1. RDBMS checks if a copy of the parsed SQL statement exists in the library cache. If parsed copy exists, then steps 2 to 6 are skipped.
2. RDBMS validates the syntax of the statement.
3. RDBMS ensures that all the columns and tables referenced in the statement exist.
4. RDBMS acquires parse locks on objects referenced in the statement so that their definitions do not change while statement is parsed.
5. RDBMS ensures that the user has sufficient privileges.
6. Statement is parsed and execution plan is created.
7. Statement is executed.
8. Values are fetched.