Oracle MERGE INTO statement behavior in concurrent sessions

A question - if we have 2 concurrent sessions executing exactly the same MERGE INTO statement on a table... what will happen? Are we going to get one row inserted, two rows inserted, one inserted and one updated... an exception... what will happen?

Well... let's see in following experiment 😏

Oracle APEX_DICTIONARY and DBA_DICTIONARY views

Oracle APEX is providing a dictionary view called APEX_DICTIONARY which is returning names and comments for all other dictionary vies.

For example:

SELECT *
FROM apex_dictionary
;

A result:

So, rows with column ID 0 contain a view name and other rows with numbers >= 1 contain column names.