CSE 511 UPDATED ACTUAL EXAM
QUESTIONS AND CORRECT ANSWERS
●● ACID
Answer: Atomicity, Consistency, Isolation and Durability
●● ACID - Atomic
Answer: All or nothing - Transaction must be completed in full or not at
all (no subdividing)
●● ACID - Consistency
Answer: Transactions will transform the database from one consistent
state to another. There are no violations of integrity constraints.
●● ACID - Isolated
Answer: Transactions execute independently of one another. Database
changes are not revealed to one another until after a transaction has
completed.
Serializable - even if some transactions are executed concurrently the
results must be the same as if they were executed serially in some order.
●● ACID - Durable
Answer: Database changes are permanent.
,●● How is concurrency achieved in DBMS?
Answer: Interleaving actions of multiple transactions.
●● Serial Schedule
Answer: Schedule that does not interleave the actions of different
transactions.
●● Equivalent Schedule
Answer: Effect of executing the first schedule is identical to the effect of
executing the second schedule.
●● Serializable Schedule
Answer: A schedule that is equivalent to some serial execution of the
transaction.
●● Two schedules are conflict equivalent if:
Answer: - Schedules involve the same actions of the same transactions
- Every pair of conflicting actions (read/write conflict) is ordered the
same way
●● Conflict Serializable Schedule
, Answer: Schedule S is conflict serializable if S is conflict equivalent to
some serial schedule.
●● Creating dependency graph to determine if transactions are conflict
serializable
Answer: -Create one node per transaction (e.g. Ti, Tj)
-Create an edge from Ti to Tj if Tj reads/writes an object last written by
Ti
-Examine the graph for cycles. If a cycle exists then the set of
transactions is NOT conflict serializable
●● Strict Two Phase Locking
Answer: A transaction must acquire a shared lock on an item before
reading and an exclusive lock on an item before writing.
-Multiple transactions may hold a shared lock on a single item.
-If a transaction holds an exclusive lock on an item no other transaction
may hold a shared/exclusive lock on that same item.
●● Define the two phases of Strict 2PL
Answer: Phase One: transaction will acquire locks that it needs
Phase Two: transaction will release locks at the end of the transaction
●● What is the lock manager?
QUESTIONS AND CORRECT ANSWERS
●● ACID
Answer: Atomicity, Consistency, Isolation and Durability
●● ACID - Atomic
Answer: All or nothing - Transaction must be completed in full or not at
all (no subdividing)
●● ACID - Consistency
Answer: Transactions will transform the database from one consistent
state to another. There are no violations of integrity constraints.
●● ACID - Isolated
Answer: Transactions execute independently of one another. Database
changes are not revealed to one another until after a transaction has
completed.
Serializable - even if some transactions are executed concurrently the
results must be the same as if they were executed serially in some order.
●● ACID - Durable
Answer: Database changes are permanent.
,●● How is concurrency achieved in DBMS?
Answer: Interleaving actions of multiple transactions.
●● Serial Schedule
Answer: Schedule that does not interleave the actions of different
transactions.
●● Equivalent Schedule
Answer: Effect of executing the first schedule is identical to the effect of
executing the second schedule.
●● Serializable Schedule
Answer: A schedule that is equivalent to some serial execution of the
transaction.
●● Two schedules are conflict equivalent if:
Answer: - Schedules involve the same actions of the same transactions
- Every pair of conflicting actions (read/write conflict) is ordered the
same way
●● Conflict Serializable Schedule
, Answer: Schedule S is conflict serializable if S is conflict equivalent to
some serial schedule.
●● Creating dependency graph to determine if transactions are conflict
serializable
Answer: -Create one node per transaction (e.g. Ti, Tj)
-Create an edge from Ti to Tj if Tj reads/writes an object last written by
Ti
-Examine the graph for cycles. If a cycle exists then the set of
transactions is NOT conflict serializable
●● Strict Two Phase Locking
Answer: A transaction must acquire a shared lock on an item before
reading and an exclusive lock on an item before writing.
-Multiple transactions may hold a shared lock on a single item.
-If a transaction holds an exclusive lock on an item no other transaction
may hold a shared/exclusive lock on that same item.
●● Define the two phases of Strict 2PL
Answer: Phase One: transaction will acquire locks that it needs
Phase Two: transaction will release locks at the end of the transaction
●● What is the lock manager?
