Noorul Islam University 2008 M.Sc Software Engineering XCS 235 – DATABASE MANAGEMENT SYSTEMS - Question Paper

retrieval operations.
77. elaborate the issues that occur in transaction if they run concurrently?
a. Lost Update issue
b. Temporary update issue
c. Incorrect summary issue
78. elaborate the kinds of failures?
a. Computer failure(system crash)
b. Transaction or system fault
c. Local errors
d. Concurrency control enforcement
e. Disk failures
f. Physical issues and catastrophes
79. elaborate the transaction operations?
a. start transaction
b. learn or write
c. End transaction
d. Commit transaction
e. Rollback or abort
80. When does a transaction reach its commit point?
A transaction T reaches its commit point when all its operations that access the
database have been executed successfully and the effect of all the transaction
operations on the database have been recorded in the log;
81. elaborate the properties of transaction?
a. Atomicity
b. Consistency reservation
c. Isolation
d. Durability or permanency
82. describe consistent state.
A consistent state of the database satisfies the constraints specified in the schema
as well as any other constraints that should hold on the database.
83. When is a schedule stated to be serial?
A schedule S is stated to be serial if, for every transaction T participating in the
schedule all the operations of T is executed consecutively in the schedule
otherwise it is non serial.
84. When is a schedule serializable?
A schedule S of transactions is serializable if it is equivalent to a few serial
schedule of the identical n transactions.
85. describe precedence graph or serialization graph?
It is a directed graph G = (n,E) that consists of a set of nodes N={T1,T2,…Tn}
and A set of directed edges E={e1,e2,…en}
86. What is a lock?
A lock is a variable associated with a data item that defines the status of the
item with respect to possible operations that can be applied to it.
87. What is a binary lock?
A binary lock can have 2 states. Locked and Unlocked.
88. elaborate the fields current in a lock?
a. Data item name
b. LOCK
c. Locking transaction
89. elaborate the locking operations of a shared/exclusive lock?
a. learn lock(X)
b. Write lock(X)

Earning:   Approval pending.