Quick Check

1.	Which isolation level or levels protect against phantom rows?
2.	Which isolation level or levels do not acquire shared locks?
3.	Where are old versions of rows in snapshot isolation stored?
4.	Which is the default isolation level?

Answers

1.	The serializable and snapshot isolation levels protect against phantom rows.
2.	Snapshot, read committed snapshot, and the read uncommitted isolation level do not acquire shared locks.
3.	Old versions of rows in snapshot isolation are stored in the tempdb system database.
4.	The read committed isolation level is the default isolation level.