Chapter 7 DBMS functions questions and answers

Chapter 7 DBMS functions questions and answers What are the functions of a DBMS? -update and retrieve data -provide catalog services -support concurrent update -recover data -provide security services -provide data integrity features -support data independence -support data replication -provide utility services What is metadata? data about data What is a data dictionary? a super catalog What is a concurrent update? multiple users make updates to the same database at the same time What is the purpose of supporting concurrent updates? ensures accuracy when several users update database at the same time what is locking? deny other users access to data while one user's updates are being processed What is transaction? set of steps completed by a DBMS to accomplish a single user task What does the two-phase locking consist of and what is its purpose? purpose is to solve lost update problem and it consists of growing phase and shrinking phase What is the growing phase? DBMS locks more rows and releases none of the locks What is the shrinking phase? DBMS releases all the locks and acquires no new locks What is the purpose of providing catalog services? to store metadata and make it accessible to users What is deadlock or deadly embrace? when two users hold a lock and require a lock on the resource that the other already has What is recovery? returning database to a correct state from an incorrect state What is journaling? maintaining a journal or log of all updates What are the most common security features used by DBMS? -encryption -authentication -authorizations -views -privacy What is encryption? converts data to a format indecipherable to another program and stores it in an encrypted format What is descrypting? reversing the encryption What is authentication? techniques for identifying the person attempting to access the DBMS What is a password? string of characters assigned by DBA to a user that must be entered for access What is biometrics? identify users by physical characteristics such as fingerprints, voice prints, handwritten signatures, and facial characteristics What are smart cards? small plastic cards with built-in circuits containing processing logic to identify the cardholder What are permissions? specify what kind of access the user has to objects in the database What are workgroups? create groups with similar permissions. Assign users to appropriate groups What is a view? snapshot of certain data in the database at a given moment in time What is privacy? right of individuals to have certain information about them kept confidential Describe a primary key constraint? must be unique, not null Describe a foreign key constraint. must match a value from primary key of another table Describe a data type. value of field must match with the data type Describe legal values. must be within prescribed bounds Describe format. 2 letters followed by 3 digits for items What are four ways of handling integrity constraints? 1. constraint is ignored 2. responsibility for constraint enforcement placed on users 3. responsibility for constraint enforcement placed on programmers 4. responsibility for constraint enforcement placed on DBMS What is data independence? can change database structure without needing to change programs that access the database What are types of database changes? -adding a field -changing a field property such as length -creating an index -adding or changing a relationship Describe Procedural language. must tell computer precisely how a given task is to be accomplished Describe non-procedural language describe task you want computer to accomplish What does DBMS allow users to do? update and retrieve data in a database without needing to know how data is structured on disk or manipulated What happens in timestamping? DBMS processes updates to a database in timestamp order