Read committed Snapshot VS Snapshot Isolation Level

Question

Could some one please help me understand when to use SNAPSHOT isolation level over READ COMMITTED SNAPSHOT in SQL Server?

I understand that in most cases READ COMMIT

Answer 1

No comparison of Snapshot and Snapshot Read Committed is complete without a discussion of the dreaded "snapshot update conflict" exception that can happen in Snapshot, but not Snapshot Read Committed.

In a nutshell, Snapshot isolation retrieves a snapshot of committed data at the start of a transaction, and then uses optimistic locking for both reads and writes. If, when attempting to commit a transaction, it turns out that something else changed some of that same data, the database will rollback the entire transaction and raise an error causing a snapshot update conflict exception in the calling code. This is because the version of data affected by the transaction is not the same at the end of the transaction as it was at the start.

Snapshot Read Committed does not suffer from this problem because it uses locking on writes (pessimistic writes) and it obtains snapshot version information of all committed data at the stat of each statement.

The possibility of snapshot update conflicts happening in Snapshot and NOT Snapshot Read Committed is an extremely significant difference between the two.