please help!!!

What happens if client A did find by primary key ( entity bean ) for a
particular record in the db.
After this another client did an update to this record.
And after him client A did again find by primary key ( entity bean )
for this record.

1.	does the entity refresh automatically ?
2.	if yes – what cause it to refresh ?
3.	does it true that when I do find by primary key it locks this
record in the db?
4.	is it lock it only for update or both select and update ?


please .

I have an interview tomorrow.

Thank a lot.