CSE 511 Midterm ACTUAL UPDATED
Exam Questions and CORRECT Answers
Transaction - CORRECT ANSWER -User program that can either read or write data from
or to the database system
ACID - CORRECT ANSWER -Atomicity, Consistency, Isolation and Durability
ACID - Atomic - CORRECT ANSWER -All or nothing - Transaction must be completed
in full or not at all (no subdividing)
ACID - Consistency - CORRECT ANSWER -Transactions will transform the database
from one consistent state to another. There are no violations of integrity constraints.
ACID - Isolated - CORRECT 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 - CORRECT ANSWER -Database changes are permanent.
How is concurrency achieved in DBMS? - CORRECT ANSWER -Interleaving actions of
multiple transactions.
Serial Schedule - CORRECT ANSWER -Schedule that does not interleave the actions of
different transactions.
Equivalent Schedule - CORRECT ANSWER -Effect of executing the first schedule is
identical to the effect of executing the second schedule.
, Serializable Schedule - CORRECT ANSWER -A schedule that is equivalent to some serial
execution of the transaction.
Two schedules are conflict equivalent if: - CORRECT 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 - CORRECT 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 - CORRECT
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 - CORRECT 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 - CORRECT 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? - CORRECT ANSWER -The lock manager handles lock and
unlock requests. These operations are atomic.
What is deadlock and how do we detect it? - CORRECT ANSWER -Cycle of transactions
waiting for locks to be released by one another.
Exam Questions and CORRECT Answers
Transaction - CORRECT ANSWER -User program that can either read or write data from
or to the database system
ACID - CORRECT ANSWER -Atomicity, Consistency, Isolation and Durability
ACID - Atomic - CORRECT ANSWER -All or nothing - Transaction must be completed
in full or not at all (no subdividing)
ACID - Consistency - CORRECT ANSWER -Transactions will transform the database
from one consistent state to another. There are no violations of integrity constraints.
ACID - Isolated - CORRECT 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 - CORRECT ANSWER -Database changes are permanent.
How is concurrency achieved in DBMS? - CORRECT ANSWER -Interleaving actions of
multiple transactions.
Serial Schedule - CORRECT ANSWER -Schedule that does not interleave the actions of
different transactions.
Equivalent Schedule - CORRECT ANSWER -Effect of executing the first schedule is
identical to the effect of executing the second schedule.
, Serializable Schedule - CORRECT ANSWER -A schedule that is equivalent to some serial
execution of the transaction.
Two schedules are conflict equivalent if: - CORRECT 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 - CORRECT 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 - CORRECT
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 - CORRECT 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 - CORRECT 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? - CORRECT ANSWER -The lock manager handles lock and
unlock requests. These operations are atomic.
What is deadlock and how do we detect it? - CORRECT ANSWER -Cycle of transactions
waiting for locks to be released by one another.
