Serializability is the strongest consistency level with regard to the execution of two concurrent transactions T1 and T2. That is, if T1 and T2 independently change the application between consistent states, and a concurrent execution of T1 and T2 is equivalent to a serial execution of T1 and T2, then that concurrent execution results in a consistent state, after committing both transactions.
For example, the following concurrent execution (time advances to the right)
T1: w(a=1) w(c=4) T2: w(a=2)w(b=3)
W(x=v) sets (i.e., writes)
x to the value
v, is equivalent to the serial execution
T1;T2, thus it is serializable and both transactions are committed.
However, it is clear that T2's write of
a causes T1's write of
a to be lost, i.e., we have a lost update despite serializability.
That is, serializability ensures consistent states in face of concurrency, though it does not prevent lost updates, which may have serious consequences (for example, imagine that T1 writes the correct delivery address of a VIP customer, and T2 writes the wrong address, T1 and T2 are run concurrently by different operators, who do not notice the mistake).
Is my statement correct about serializability and lost updates?
If it is correct then the table in "Isolation levels, read phenomena, and locks" in this wiki page can only be wrong with regard to serializability and lost updates.
If so, what other stronger consistency level ensures that there are no lost updates?