WorksheetsTransactions 2: Serializability
Total questions: 15
Worksheet time: 9mins
A (possibly concurrent) schedule is serializable if it is ....
executed in a real time manner
always gives the same result
executed serially
equivalent to a serial schedule
We can identify a serializable schedule by checking the following notions ...
Conflict serializability
View serializability
Recoverable serializability
Concurrent serializability
The following instructions are conflicts if executed consecutively, except..
li = read(Q), lj = read(Q)
li = read(Q), lj = write(Q)
li = write(Q), lj = read(Q)
li = write(Q), lj = write(Q)
If a schedule S can be transformed into a schedule S’ by a series of swaps of non-conflicting instructions, we say that S and S’ are ..
conflict serializable
conflict equivalent
conflict serializability
conflict
A schedule S that conflict equivalent to a serial schedule is called ..
conflict serializable
conflict equivalent
conflict serializability
conflict
Examine the following schedules.
Schedule 3 is conflict serializable.
True
False
Examine the following schedule.
The schedule is not conflict serializable.
True
False
Let S and S’ be two schedules with the same set of transactions. S and S’ are view equivalent if the following three conditions are met, for each data item Q,
The transaction (if any) that performs the final write(Q) operation in schedule S must also perform the final write(Q) operation in schedule S’.
If in schedule S, transaction Ti reads the initial value of Q, then in schedule S’ also transaction Ti must read the initial value of Q
If in schedule S transaction Ti executes read(Q), and that value was produced by transaction Tj (if any), then in schedule S’ also transaction Ti must read the value of Q that was produced by the same write(Q) operation of transaction Tj .
If in schedule S, transaction Ti write the initial value of Q, then in schedule S’ also transaction Ti must write the initial value of Q
Every view serializable schedule is also conflict serializable
True
False
The following schedule is not a recoverable schedule.
True
False
A single transaction failure leads to a series of transaction rollbacks. The incident is called ...
Concurrent Rollback
Serial Rollback
Cascading Rollback
Parallel Rollback
Every cascade-less schedule is not recoverable.
True
False
The weakest level of consistency is ...
Serializable
Read Committed
Read Uncommitted
Repeatable Read
The strongest level of consistency is ...
Serializable
Read Committed
Read Uncommitted
Repeatable Read
The following schedule is view serializable.
True
False
