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UTA INSY 3304 - Chapter 10 With 100% Correct Solutions Latest Update
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UTA INSY 3304 - Chapter 10 With 100% CorrectSolutions Latest Update
Transaction - ANSWER A logical unit of work that must be entirely completed or aborted
Atomicity - ANSWER All operations of a transaction must be completed; if not the
transaction is aborted
Consistency - ANSWER Permanence of database's consistent state
Isolation - ANSWER Data used during transaction cannot be used by second transaction
until the first is completed
Durability - ANSWER Ensures that once transactions are committed they cannot be
undone or lost
Serializability - ANSWER Ensures that the schedule for the concurrent execution of
multiple transactions must produce consistent results
Transaction Log - ANSWER Records all transactions that modify the database
DBMS utilizes information stored in a log in case of: a) Recovery requirement initiated by
a ROLLBACK statement
b) Abnormal termination of a program
c) System failure
Concurrency Control- ANSWER Coordination of execution of simultaneously running
transactions in a multiuser database system
, • Objective: ensures serializability of transactions in a multiuser database environment
Problems in Concurrency Control - ANSWER Lost update, uncommitted data,
inconsistent retrievals
Scheduler - ANSWER Establishes the order in which the operations are executed within
concurrent transactions
- Creates serialization schedule
Locking methods - ANSWER facilitate isolation of data items used in concurrently
executing transactions
Lock - ANSWER guarantees exclusive use of a data item to a current transaction
Pessimistic locking - ANSWER use of locks based on the assumption that conflict
between transactions is likely
Lock manager - ANSWER responsible for assigning and policing the locks used by the
transactions
Lock Granularity - ANSWER - indicates level of lock use
- levels: database, table, page, row, or field (attribute)
Binary lock A lock which has only two states, namely, locked (1) and unlocked (0). If a
data item is locked by a transaction, no other transaction is allowed to use the data item.
Exclusive lock An access which is reserved for the transaction that has locked the
object
Shared lock All the concurrent transactions are granted read access on the basis of a
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