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GK One-Line Question & Answer

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DBMS → Indexes 3

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
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Snapshot isolation is used to give
transaction a snapshot of the database and database a snapshot of committed values in the transaction
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The assumption that hardware errors and bugs in the software bring the system to a halt, but do not corrupt the nonvolatile storage contents, is known as the
fail-stop assumption
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DBMS → Transactions 3

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
wound-wait
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Lost update problem is
second update overwrites the first
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The database is partitioned into fixed- length storage units called
blocks
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DBMS → Concurrency Control 3

The situation where the lock waits only for a specified amount of time for another lock to be released is
lock timeout
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Each of a pair of transactions has read data that is written by the other, but there is no data written by both transactions, is referred to as
none of the mentioned
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The log is a sequence of                     recording all the update activities in the database.
log records
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DBMS → Deadlock 3

The deadlock in a set of a transaction can be determined by
read-only graph
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Which statements are correct regarding indexes?
all of the mentioned
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In the                        scheme, a transaction that wants to update the database first creates a complete copy of the database.
shadow copy
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DBMS → Database Security 2

A deadlock exists in the system if and only if the wait-for graph contains a                        
cycle
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A non-correlated subquery can be defined as                 
a set of one or more sequential queries in which generally the result of the inner query is used as the search value in the outer query
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DBMS → PL/SQL 2

                     rollback requires the system to maintain additional information about the state of all the running transactions.
partial
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Which statement is true regarding synonyms?
a public synonym and a private synonym can exist with the same name for the same table
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DBMS → Introduction to DBMS 2

If a node is locked in an intention mode, explicit locking is done at a lower level of the tree. This is called
intention lock modes
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The method of access that uses key transformation is called as
hash
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DBMS → Database Architecture 2

If a node is locked in                      explicit locking is being done at a lower level of the tree, but with only shared-mode locks.
intention lock modes
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Why do we need concurrency control on B+ trees ?
to maintain accuracy of index
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DBMS → Data Models 2

If a node is locked in                          then explicit locking is being done at a lower level, with exclusive-mode or shared-mode locks.
intention-exclusive (ix) mode
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How many techniques are available to control concurrency on B+ trees?
none of the mentioned
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DBMS → ER Model 2

If a node is locked in                              the subtree rooted by that node is locked explicitly in shared mode, and that explicit locking is being done at a lower level with exclusive-mode locks.
shared and intention-exclusive (six) mode
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In crabbing protocol locking
goes down the tree and back up
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DBMS → Relational Model 2

The                      requires that each transaction Ti executes in two or three different phases in its lifetime, depending on whether it is a read-only or an update transaction.
validation protocol
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The deadlock can be handled by
restarting the search after releasing the lock
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DBMS → Normalization 2

                         denotes the largest timestamp of any transaction that executed write(Q) successfully.
w-timestamp(q)
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In crabbing protocol, the lock obtained on the root node is in                    mode.
shared
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DBMS → Functional Dependency 2

The most recent version of standard SQL prescribed by the American National Standards Institute is
sql 2016
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If needed to split a node or coalesce it with its siblings, or redistribute key values between siblings, the crabbing protocol locks the parent of the node in                           mode.
exclusive
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DBMS → SQL Basics 2

ANSI-standard SQL allows the use of special operators in conjunction with the WHERE clause. A special operator used to check whether an attribute value is null is
is null
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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.
key-value locking
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DBMS → DDL Commands 2

A lock that prevents the use of any tables in the database from one transaction while another transaction is being processed is called a
database-level lock
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The recovery scheme must also provide
high availability
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DBMS → DML Commands 2

A condition that occurs when two transactions wait for each other to unlock data is known as a(n)
deadlock
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Which one of the following is a failure to a system
transaction failure
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DBMS → Joins 2

The extent of the database resource that is included with each lock is called the level of
granularity
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The system has entered an undesirable state (for example, deadlock), as a result of which a transaction cannot continue with its normal execution. This is
logical error
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DBMS → Views 2

DBMS periodically suspends all processing and synchronizes its files and journals through the use of
checkpoint facility
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The transaction can no longer continue with its normal execution because of some internal condition, such as bad input, data not found, overflow, or resource limit exceeded. This is
logical error
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