The following multiversion concurrency control has been proposed.
Reads are satisfied using the (committed) version of the database that existed when
the transaction made its first read request. Writes are controlled by long-duration
write locks on tables.
Does the control always produce serializable schedules? If not, give a nonserializable
schedule it might produce.
The control can produce schedules with both write skew and lost updates. Assume x
and y are in different tables.
Write Skew:
r1(x) r1(y) r2(x) r2(y) w1(x) w2(y)
Lost Update:
r1(x) r2(x) w1(x) commit1 w2(x)
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