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CUSTOMER_CODE SMUDE DIVISION_CODE SMUDE EVENT_CODE APR2016 ASSESSMENT_CODE BT0066_APR2016 QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 73047 QUESTION_TEXT Explain data base manager, database administrator & data dictionary SCHEME OF EVALUATION Database Manager: The program module called Database manager is the one which provides interface between row data stored in the database and application programs. The queries are submitted to the system through the application. One of the main responsibilities of database manager is to provide interface with file system… Database Administrator: A major reason for a database management system is to have control over data and programs access to these data. Such people we call database administrator (DBA)… Data Dictionary It is extremely difficult to keep track of all available names and also the purpose of using these names, as size of the program increases in larger. Only the programmer can keep in mind regarding the available names. QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 73048 QUESTION_TEXT Explain magnetic disks along with its physical characteristics, performance measures & optimization of disc block access. Magnetic Disks SCHEME OF EVALUATION The magnetic disks facilitate the bulk of secondary storage. In the modern computer systems the storage capacity requirements have been growing at over 50 percent per year. Physical Characteristics of Disks Each disk platter has a flat circular shape. Its two surfaces are covered with a magnetic material, and information is recorded on the surfaces. Platters are made from rigid metal or glass and are covered (usually on both sides) with magnetic recording material. The disk surface is logically divided into tracks, which are subdivided into sectors. A sector is the smallest unit of information that can be read from or written to the disk. Performance Measures of Disks The quality of a disk can be measured by its access time, capacity, reliability and data-transfer-rate. Access time is the time from when a read or write request is issued to when data transfer begins. 4 Optimization of Disk-Block Access In most of the operating system the disk I/O request generated by file system and by virtual memory manager. Here the request provides address on the disk and this address is in the form of a block number. A block is a contiguous sequence of sectors from a single track of one platter. QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 73049 QUESTION_TEXT Explain E.R model. SCHEME OF EVALUATION The Entity-Relationship Model In conceptual schema we make use of tool called entity-relationship model to represent and analyze the features of an application. Entityrelationship model approach includes a graphical notation, where entity represent as rectangle shape, relationship as diamond shape, and attributes as oval or circle shape… This is the best tool for transition from an information application description to a formal database schema. In an enterprise entityrelationship model is used for describing the conceptual schema. The description of physical schema not defined at this stage. The entityrelationship diagram is then used to design logical schema in which the database is actually implemented… QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 118248 QUESTION_TEXT What are the alternative object oriented database strategies? Explain them - Novel database data model Extending an existing database language with objectorientation capabilities SCHEME OF EVALUATION Extending an existing object-oriented programming language with database capabilities Embedding object-oriented database language constructs in a host language All 4 to be explained & each carries 2.5 marks QUESTION_T DESCRIPTIVE_QUESTION YPE QUESTION_ID 163210 QUESTION_T Explain the anomalies in a database. EXT Anomalies in a Database Let us consider a relation schema regarding the information about an employee of an organization. SCHEME OF EVALUATION EMP_PROJ(Ssn, Pnumber, Hours, Ename, Pname,Plocation) Tuples of a relation on the relation schema EMP_PROJ(Ssn, Pnumber, Hours, Ename, Pname, Plocation) are shown in Table 9.2. Figure 9.3 shows the functional dependencies among its attributes. The key attributes of the relation are Ssn, Pnumber. Function dependencies of the relation { Ssn, Pnumber Hours, Ssn Ename, Pnumber Pname, Plocation} Table 9.2: Employee Data Representation in Relation EMP_PROJ Attribute Ename is not functionally dependent on the whole key, but partially depend on the one of the key namely Ssn. Similarly Pname and plocation partially depends on attribute Pnumber. Only the attribute Hours is fully functionally dependent on the key Ssn, Pnumber. There are several undesirable problems in relation schema EMP_PROJ. Redundancy: The objective of the database system is to reduce duplicate data being stored in database, which in turn leads to waste of storage space, increases the size of the data stored and also some time leads to inconsistencies among the data. Whenever an update operation conducted on a database with high redundancies this leads to inconsistent state which are explained below. Table 9.2 contain attributes Pname and Plocation of project are stored several times where one of employee and another for project. Update Anomalies: Update anomalies are occurs when multiple copies of same fact exist in the database. This also leads to inconsistencies, when only some of many copies are updated. Consider relation schema Figure 9.3 a change in the Plocation of project number 2 made consistent in all the tuples related to project number 2. If the update is not reflected one of the three tuples then there will be an inconsistency in the data. Insertion Anomalies: In the given relation schema we cannot enter only project name & location for a given project number and this not meant for . We need to have employee with proper SSN to him. Deletion Anomalies: Given the project an individual employee wants to discontinue, there is always possibility that we may lose information regarding project name and its location. And this could happen if we maintain single relation which maintains all these information in it. If we have another relation for project information then deletion of any tuple from EMP_PROJ will not cause any information lost. QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 163211 QUESTION_TEXT When BCNF is needed? Explain BCNF. Boyce-Codd Normal Form (BCNF) Consider a composite key attribute in a relation which having common attribute. If there exist any dependency among the attribute of composite key then that relation require a normalization called BCNF. Let us consider an example, the relation Employee: Employee (Employee code, Project, Project head, Percent time) SCHEME OF EVALUATION Let us assume that 1. An employee can work more than one project 2. Percentage of hours he/she works for each project is given. 3. Each project monitored by project head. …………………………………………..