CS8492 DBMS IAT 2 PART B

Instead of locking index leaf nodes in a two-phase manner, some index concurrency-control schemes use ___________ on individual key values, allowing other key values to be inserted or deleted from the same leaf.

• B+ tree locking

• Link level locking

• Key-value locking

• Next value locking

When transaction Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp smaller than that of Tj (that is, Ti is older than Tj). Otherwise, Ti is rolled back (dies). This is

• Wait-die

• Wait-wound

• Wound-wait

• Wait

When transaction Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp larger than that of Tj (that is, Ti is younger than Tj ). Otherwise, Tj is rolled back (Tj is wounded by Ti). This is

• Wait-die

• Wait-wound

• Wound-wait

• Wait

Selecting the victim to be rollbacked to the previous state is determined by the minimum cost. The factors determining cost of rollback is

• How long the transaction has computed, and how much longer the transaction will compute before it completes its designated task

• How many data items the transaction has used

• How many more data items the transaction needs for it to complete

• All of the mentioned

If transaction Ti gets an explicit lock on the file Fc in exclusive mode, then it has an ­­­­­­__________ on all the records belonging to that file.

• Explicit lock in exclusive mode

• Implicit lock in shared mode

• Explicit lock in shared mode

• Implicit lock in exclusive mode

Constraint checking can be disabled in existing _______________ and _____________ constraints so that any data you modify or add to the table is not checked against the constraint.

• CHECK, FOREIGN KEY

• DELETE, FOREIGN KEY

• CHECK, PRIMARY KEY

• PRIMARY KEY, FOREIGN KEY

If a multivalued dependency holds and is not implied by the corresponding functional dependency, it usually arises from one of the following sources.

• A many-to-many relationship set

• A multivalued attribute of an entity set

• A one-to-many relationship set

• Both A many-to-many relationship set and A multivalued attribute of an entity set

We can use the following three rules to find logically implied functional dependencies. This collection of rules is called

• Axioms

• Armstrong’s axioms

• Armstrong

• Closure

The relation employee(ID,name,street,Credit,street,city,salary) is decomposed into

employee1 (ID, name)

employee2 (name, street, city, salary)

This type of decomposition is called

• Lossless decomposition

• Lossless-join decomposition

• All of the mentioned

• None of the mentioned

There are two functional dependencies with the same set of attributes on the left side of the arrow:

A->BC

A->B

This can be combined as

• A->BC

• A->B

• B->C

• None of the mentioned