Download UNIT-I PART – A List out the different levels in database tuning

UNIT-I
PART – A
1. List out the different levels in database tuning.
2014)
 Tuning of hardware
 Tuning of schema
 Tuning of indices
 Tuning of materialized views
 Tuning of transactions
(May/June
2. Give the ACID properties
(May/June
2014)
The four basic ACID Properties of a transaction are
•
Atomicity
•
Consistency
•
Isolation
•
Durability
3. What is lock de escalation and under what condition it is necessary?
(May/June
2014)
If the client does not need a prefetched item, it can transfer locks on the items back to the
server, and the lock can be allocated to other clients
4. What do you mean by concurrency control?
2014)
To be resistant to site and communication failure.
To permit parallelism to satisfy performance requirements.
To place few constraints on the structure of atomic actions.
(May/June
5. Comapre RDBMS and ORDBMS.
2014)
RDBMS
Semantic overloading.
Poor representation of ‘real world’ entities
Poor support for integrity & business constraints.
(May/June
Homogeneous data structure.
Limited operations.
Difficulty handling recursive queries.
Difficulty with ‘Long Transactions
ORDBMS
An Object-Relational database adds features associated with object-oriented
systems to a RDBMS
User-extensible type system
Encapsulation
Inheritance
Polymorphism
Dynamic binding of methods
Complex objects including first normal form objects
Object Identity
PART – B
1.
2.
Construct an E-R diagram for a hospital with a set of patients and a set of medical
doctors.Associate with each patient a log of the various tests and examination conducted.
(Nov/Dec 2011)
(8)
Devise a timestamp-based protocol that avoids the phantom phenomenon. (Nov/Dec
2011)
(8)
Timestamp Ordering Algorithm
ü
Basic Timestamp Ordering
ü
Strict Timestamp Ordering
ü
Thomas's Write Rule
The idea for this scheme is to order the transactions based on their timestamps. A schedule in
which the transactions participate is then serializable, and the equivalent serial schedule has the
transactions in order of their timestamp values. This is called timestamp ordering (TO). Notice
how this differs from 2PL, where a schedule is serializable by being equivalent to some serial
schedule allowed by the locking protocols. In timestamp ordering, however, the schedule is
equivalent to the particular serial order corresponding to the order of the transaction
timestamps. The algorithm must ensure that, for each item accessed by conflicting operations in
the schedule, the order in which the item is accessed does not violate the serializability order. To
do this, the algorithm associates with each database item X two timestamp (TS) values:
1. Read_TS(X): The read timestamp of item X; this is the largest timestamp among all the
timestamps of transactions that have successfully read item X—that is, read_TS(X) = TS(T),
where T is the youngest transaction that has read X successfully.
2.Write_TS(X): The write timestamp of item X; this is the largest of all the timestamps of
transactions that have successfully written item X—that is, write_TS(X) = TS(T), where T is the
youngest transaction that has written X successfully.
3. Briefly explain the types of joint operation in query processing with an example for
each.(Nov/Dec 2011)
(16)
Theta (θ) Join
Theta join combines tuples from different relations provided they satisfy the theta condition. The
join condition is denoted by the symbol θ.
Notation R1 ⋈θ R2
R1 and R2 are relations having attributes (A1, A2, .., An) and (B1, B2,.. ,Bn) such that the
attributes don’t have anything in common, that is R1 ∩ R2 = Φ.
Equijoin
When Theta join uses only equality comparison operator, it is said to be equijoin. The above
example corresponds to equijoin.
Natural Join (⋈)
Natural join does not use any comparison operator. It does not concatenate the way a Cartesian
product does. We can perform a Natural Join only if there is at least one common attribute that
exists between two relations. In addition, the attributes must have the same name and domain
Outer Joins
Theta Join, Equijoin, and Natural Join are called inner joins. An inner join includes only those
tuples with matching attributes and the rest are discarded in the resulting relation. Therefore, we
need to use outer joins to include all the tuples from the participating relations in the resulting
relation. There are three kinds of outer joins − left outer join, right outer join, and full outer join.
Left Outer Join(R Left Outer Join S)
All the tuples from the Left relation, R, are included in the resulting relation. If there are tuples in
R without any matching tuple in the Right relation S, then the S-attributes of the resulting
relation are made NULL.
Right Outer Join: ( R Right Outer Join S )
All the tuples from the Right relation, S, are included in the resulting relation. If there are tuples
in S without any matching tuple in R, then the R-attributes of resulting relation are made NULL.
Full Outer Join: ( R Full Outer Join S)
All the tuples from both participating relations are included in the resulting relation. If there are
no matching tuples for both relations, their respective unmatched attributes are made NULL.
3. (i) Discuss 1NF,2NF,3NF (April/May 2011) (May/June 2014)
(10)
Normalization rule are divided into following normal form.
 First Normal Form
 Second Normal Form
 Third Normal Form
 BCNF
Database Normalization is a technique of organizing the data in the database. Normalization is a
systematic approach of decomposing tables to eliminate data redundancy and undesirable
characteristics like Insertion, Update and Deletion Anomalies. It is a multi-step process that puts
data into tabular form by removing duplicated data from the relation tables.
Normalization is used for mainly two purpose,
Eliminating reduntant(useless) data
Ensuring data dependencies make sense i.e data is logically stored.
Updation Anamoly : To update address of a student who occurs twice or more than twice in a
table, we will have to update S_Address column in all the rows, else data will become
inconsistent.
Insertion Anamoly : Suppose for a new admission, we have a Student id(S_id), name and
address of a student but if student has not opted for any subjects yet then we have to insert
NULL there, leading to Insertion Anamoly.
Deletion Anamoly : If (S_id) 401 has only one subject and temporarily he drops it, when we
delete that row, entire student record will be deleted along with it.
4.
Discuss
(April/May 2011)
(16)
(i) Conflict serializability
The following observation is a key characterization of conflict serializability: A schedule
is conflict-serializable if and only if its precedence graph of committed transactions
(when only committed transactions are considered) is acyclic.
(ii) View serializability
Two schedules S1 and S2 are view equivalent if
they involve the same set of actions of the same transactions and
if Ti reads the initial value of X in S1 then it must also read the initial value of X in S2
and
if Ti reads the value of X written by Tj in S1 then it must also read the value of X written
by Tj in S2 and
For each data object X, the transaction (if any) that performs the final write on X in S1
must also perform the final write on X in S2
(iii) Two phase commit protocol
The commit-request phase (or voting phase)
Completion phase
(iv) Validation based concurrency control protocol
Execution of transaction Ti is done in three phases.
1. Read and execution phase: Transaction Ti writes only to
temporary local variables
2. Validation phase: Transaction Ti performs a ``validation test''
to determine if local variables can be written without violating
serializability.
3. Write phase: If Ti is validated, the updates are applied to the
database; otherwise, Ti is rolled back.
The three phases of concurrently executing transactions can be interleaved, but each
transaction must go through the three phases in that order.
Also called as optimistic concurrency control since transaction executes fully in the hope
that all will go well during validation
 Start(Ti) : the time when Ti started its execution
 Validation(Ti): the time when Ti entered its validation phase
 Finish(Ti) : the time when Ti finished its write phase
5. Explain the deferred and immediate modification versions of log based recovery
scheme May/June 2014 (8)