Transaction stages supported by SQL Server

Question

Describe the meaning of each of the transaction stages supported by SQL Server?

Answer 1

The strictest isolation stage is SERIALIZABLE. By using it, SQL Server places a range lock on the rows which have been read. This stage is the most expensive to employ and should only be employed when absolutely required. The next most restrictive stage is REPEATABLE READ, which signifies SQL Server places and holds locks on all rows which are read. It is possible to make unclean reads by setting the isolation stage to READ UNCOMMITTED that is the least restrictive level is the default isolation stage is READ COMMITTED.