CS403 - Database Management Systems
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Q & A
Short Question & Answers
Q1: Define domain of an attribute.
We have discussed in the previous section that every attribute has got a name. Next thing is that a domain is also associated with an attribute. These two things, name and the domain, are part of the definitions of an attribute and we must provide them. Domain is the set of possible values that an attribute can have, that is, we specify a set of values either in the form of a range or some discrete values, and then attribute can have value out of those values. Domain is a form of a check or a constraint on attribute that it cannot have a value outside this set.
Q2: Write the main feature of volatile storage media?
Computer storage that is lost when the power is turned off is called as volatile storage.
Q3: What is the difference between a primary key and a unique key with reference to clustered and non-clustered indexes?
Primary Indexes: Consider a table, with a Primary Key Attribute being used to store it as an ordered array (that is, the records of the table are stored in order of increasing value of the Primary Key attribute.)As we know, each BLOCK of memory will store a few records of this table. Since all search operations require transfers of complete blocks, to search for a particular record, we must first need to know which block it is stored in. If we know the address of the block where the record is stored, searching for the record is very fast. Notice also that we can order the records using the Primary Key attribute values. Thus, if we just know the primary key attribute value of the first record in each block, we can determine quite quickly whether a given record can be found in some block or not. This is the idea used to generate the Primary Index file for the table. Users often need to access data on the basis of non-key or non-unique attribute; secondary key. Like student name, program name, students enrolled in a particular program .Records are stored on the basis of key attribute; three possibilities. However, we have already ordered the records of our table using the Primary key. We cannot order the records again using the secondary key (since that will destroy the utility of the Primary Index Therefore, the Secondary Index is a two column file, which stores the address of every tuple of the table.
Q4: Name the five main components of Database management systems software.
DBMS Engine accepts logical request from the various other DBMS subsystems, converts them into physical equivalents, and actually accesses the database and data dictionary as they exist on a storage device. Data Definition Subsystem helps user to create and maintain the data dictionary and define the structure of the files in a database. Data Manipulation Subsystem helps user to add, change, and delete information in a database and query it for valuable information. Software tools within the data manipulation subsystem are most often the primary interface between user and the information contained in a database. It allows user to specify its logical information requirements. Application Generation Subsystem contains facilities to help users to develop transaction-intensive applications. It usually requires that user perform a detailed series of tasks to process a transaction. It facilitates easy-to-use data entry screens, programming languages, and interfaces. Data Administration Subsystem helps users to manage the overall database environment by providing facilities for backup and recovery, security management, query optimization, concurrency control, and change management.
Q5: What is meant by database recovery services?
We are discussing the deferred updates approach regarding the database recovery techniques. In the previous lecture we studied the structure of log file entries for the deferred updates approach. In today’s lecture we will discuss the recovery process.
Q6: What is Sequence?
First we see what the sequence of actions is when a write operation is performed. On encountering a ‘write’ operation, the DBMS places an entry in the log file buffer mentioning the effect of the write operation. For example, if the transaction includes the operations: X = X + 10 Write X Supposing that the value of X before the addition operation is 23 and after the execution of operation it becomes 33. Now against the write operation, the entry made in the log file will be
Q7: Write four steps to recover from a deadlock between the transactions.
Following are some of the approaches for the deadlock handling: Deadlock prevention, Deadlock detection and resolution, Prevention is not always possible, Deadlock is detected by wait-for graph.
Q8: Write five advantages of using VIEWS.
The fields that appear in the view. The column title for each field in the view. The order of the fields in the view. The width of columns in the view, as well as the overall width of the view. The set of records that appear in the view (Filtering). The order in which records are displayed in the view (Sorting & Grouping). Column totals for numeric and currency fields (Totaling & Subtotaling).
Q9: What do you know about Insertion anomaly?
Insertion anomaly indicates that we cannot insert a fact about one entity until we have an additional fact about another entity.
Q10: Define domain of an attribute.
In computing, the attribute domain is the set of values allowed in an attribute. For the relational model it is a requirement that each part of a tuple be atomic. The consequence is that each value in the tuple must be of some basic type, like a string or an integer. For the elementary type to be atomic it cannot be broken into more pieces.
Course Instructor

Dr. Nayyer Masood
Ph.D Computer Science Bradford University, UK

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