Chapter 7 – Concepts of Database Management
occurs when multiple users make updates to the database at the same time
Periodically, usually once a day, a single update program reads the batch of records in this file one at a time and performs the appropriate updates to the database; this processing technique is called
denies other users access to data while the DBMS processes one user’s updates to the database
a set of steps completed by a DBMS to accomplish a single user task; the DBMS must successfully complete all these steps or none at all for the database to remain in a correct state
Two Phase Locking
Consists of Growing Phase and Shrinking phase to avoid the lost update problem
when the DBMS locks more rows and releases none of the locks
when the DBMS releases all the locks and acquires no new locks
When two people are accessing a record and trying to update it as well as the other locked one.
To break this one option would be to have the DBMS detect and break the deadlock. The DBMS would choose one deadlocked user to be the
alternative to two phase locking. the DBMS assigns to each database update the unique time when the update started
the process of returning the database to a state that is known to be correct from a state known to be incorrect
enterprise DBMS provide sophisticated features to avoid the costly and time-consuming process of having users redo their work. These features include _____________. Involves maintaining a log of all updates to the database
Before and After Image
Logs include two images and an entry. What are these called
includes a record of what the data in the row looked like in the database before the update
includes a record of what the data in the row looked like in the database after the update
the log contains an entry to indicate the start of a transaction and the successful completion ____________ of a transaction
is used when the database has been destroyed and uses after images of committed transactions from the log to bring the database up to date
is used if the database has not actually been destroyed but the problem must involve transactions that were either incorrect or, more likely stopped midstream.
converts the data in a database to a format that is indecipherable by a word processor or another program and stores it in ______________format
reverses the encryption
refers to techniques for identifying the person who is attempting to access the DBMS.
The database administrator uses _________ ________ that specify which users have what type of access to which data in the database
specify what kind of access the user has to objects in the database.
The DBA usually creates groups of users, sometimes called ______________; assigns the appropriate permissions to each group; and then assigns each user to the appropriate group based on the permissions the user requires
Passwords, Bio-metrics, Smart Cards, Database Password
Techniques for identifying the person attempting to access the DBMS. Forms of Authentication
Identify users by physical characteristics such as fingerprints, voiceprints, handwritten signatures, and facial characteristics.
small plastic cards with built-in circuits containing processing logic to identify the cardholder
String of characters assigned by a DBA to a user that must be entered for access
string of characters assigned to database that users must enter for accessing the database
snapshot of certain data in the database at a given moment in time(Can be used for security purposes)
Can change database structure without needing to change programs that access the database
DBMS exchanges all updated data between master database and a replica
assist in general database management
Must tell computer precisely how a given task is to be accomplished
Non Procedural Language
describe task you want computer to accomplish