This property is called durability. What do you mean by atomicity and aggregation? Atomicity: Either all actions are carried out or none are. Users should not have to worry about the effect of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions. Aggregation: A concept which is used to model a relationship between a collection of entities and relationships.
It is used when we need to express a relationship among relationships. What is a Phantom Deadlock? In distributed deadlock detection, the delay in propagating local information might cause the deadlock detection algorithms to identify deadlocks that do not really exist. Such situations are called phantom deadlocks and they lead to unnecessary aborts. What is a checkpoint and when does it occur? By taking checkpoints, the DBMS can reduce the amount of work to be done during restart in the event of subsequent crashes.
What are the different phases of transaction? What do you mean by flat file database? It is a database in which there are no programs or user access languages. It has no cross- file capabilities but is user-friendly and provides user-interface management. What is "transparent DBMS"? It is one, which keeps its Physical Structure hidden from user. Brief theory of Network, Hierarchical schemas and their properties Network schema uses a graph data structure to organize records example for such a database management system is CTCG while a hierarchical schema uses a tree data structure example for such a system is IMS.
What is a query? A query with respect to DBMS relates to user commands that are used to interact with a data base. The query language can be classified into data definition language and data manipulation language. What do you mean by Correlated subquery? Subqueries, or nested queries, are used to bring back a set of rows to be used by the parent query. Depending on how the subquery is written, it can be executed once for the parent Dept.
If the subquery is executed for each row of the parent, this is called a correlated subquery. A correlated subquery can be easily identified if it contains any references to the parent subquery columns in its WHERE clause.
Columns from the subquery cannot be referenced anywhere else in the parent query. The following example demonstrates a non-correlated subquery. CNUM What are the primitive operations common to all record management systems? Addition, deletion and modification. What are the unary operations in Relational Algebra? JOIN: Concatenation of rows from one relation and related rows from another. Two important pieces of RDBMS architecture are the kernel, which is the software, and the data dictionary, which consists of the system-level data structures used by the kernel to manage the database You might think of an RDBMS as an operating system or set of subsystems , designed specifically for controlling data access; its primary functions are storing, retrieving, and securing data.
An RDBMS maintains its own list of authorized users and their associated privileges; manages memory caches and paging; controls locking for concurrent resource usage; dispatches and schedules user requests; and manages space usage within its table-space structures.
How Data dictionary is a set of tables and database objects that is stored in a special area of the database and maintained exclusively by the kernel. What is the job of the information stored in data-dictionary? The information in the data dictionary validates the existence of the objects, provides access to them, and maps the actual physical storage location.
Not only RDBMS takes care of locating data it also Determines an optimal access path to store or retrieve the data Define SQL and state the differences between SQL and other conventional programming Languages SQL is a nonprocedural language that is designed specifically for data access operations on normalized relational database structures.
The primary difference between SQL and other conventional programming languages is that SQL statements specify what data operations should be performed rather than how to perform them.
Name the three major set of files on disk that compose a database in Oracle There are three major sets of files on disk that compose a database. All the files are binary. The control files and the redo logs support the functioning of the architecture itself. All three sets of files must be present, open, and available to Oracle for any data on the database to be useable.
Without these files, you cannot access the database, and the database administrator might have to recover some or all of the database using a backup, if there is one. What is an Oracle Instance? The Oracle system processes, also known as Oracle background processes, provide functions for the user processes—functions that would otherwise be done by the user processes themselves Dept.
The data and control structures in the SGA are shareable, and all the Oracle background processes and user processes can use them. What are database files, control files and log files. How many of these files should a database have at least? Database Files The database files hold the actual data and are typically the largest in size.
Depending on their sizes, the tables and other objects for all the user accounts can go in one database file—but that's not an ideal situation because it does not make the database structure very flexible for controlling access to storage for different users, putting the database on different disk drives, or backing up and restoring just part of the database.
You must have at least one database file but usually, more than one files are used. In terms of accessing and using the data in the tables and other objects, the number or location of the files is immaterial.
The database files are fixed in size and never grow bigger than the size at which they were created ControlFiles The control files and redo logs support the rest of the architecture. Any database must have at least one control file, although you typically have more than one to guard against loss. The control file records the name of the database, the date and time it was created, the location of the database and redoes logs, and the synchronization information to ensure that all three sets of files are always in step.
Every time you add a new database or redo log file to the database, the information is recorded in the control files. These are the journals for the database; the redo logs record all changes to the user objects or system objects. If any type of failure occurs, the changes recorded in the redo logs can be used to bring the database to a consistent state without losing any committed transactions.
In the case of non-data loss failure, Oracle can apply the information in the redo logs automatically without intervention from the DBA. The redo log files are fixed in size and never grow dynamically from the size at which they were created. Once assigned when the row is first inserted into the database , it never changes until the row is deleted or the table is dropped.
The ROWID consists of the following three components, the combination of which uniquely identifies the physical storage location of the row.
What is Oracle Block? Can two Oracle Blocks have the same address? Oracle "formats" the database files into a number of Oracle blocks when they are first created—making it easier for the RDBMS software to manage the files and easier to read data into the memory areas. The block size should be a multiple of the operating system block size.
Regardless of the block size, the entire block is not available for holding data; Oracle takes up some space to manage the contents of the block. This block header has a minimum size, but it can grow. These Oracle blocks are the smallest unit of storage. Increasing the Oracle block size can improve performance, but it should be done only when the database is first created. Each Oracle block is numbered sequentially for each database file starting at 1.
Two blocks can have the same block address if they are in different database files. What is database Trigger? The trigger can e defined to execute once for the entire statement or once for every row that is inserted, updated, or deleted. For any one table, there are twelve events for which you can define database triggers. Name two utilities that Oracle provides, which are use for backup and recovery.
These utilities are Exportand Import. The Export utility dumps the definitions and data for the specified part of the database to an operating system binary file. The Import utility reads the file produced by an export, recreates the definitions of objects, and inserts the data If Export and Import are used as a means of backing up and recovering the database, all the changes made to the database cannot be recovered since the export was performed.
The best you can do is recovering the database to the time when the export was last performed. What are stored-procedures? And what are the advantages of using them.
Stored procedures are database objects that perform a user defined operation. A stored procedure can have a set of compound SQL statements. A stored procedure executes the SQL commands and returns the result to the client.
Stored procedures are used to reduce network traffic. Spurious tuples may occur due to i. Bad normalization ii. Theta joins iii. A dominant entity is the entity a on the N side in a 1 : N relationship b on the 1 side in a 1 : N relationship c on either side in a 1 : 1 relationship d nothing to do with 1 : 1 or 1 : N relationship b on the 1 side in a 1 : N relationship What is Storage Manager? It is a program module that provides the interface between the low-level data stored in database, application programs and queries submitted to the system.
What is Buffer Manager? It is a program module, which is responsible for fetching data from disk storage into main memory and deciding what data to be cache in memory. What is Transaction Manager? It is a program module, which ensures that database, remains in a consistent state despite system failures and concurrent transaction execution proceeds without conflicting. What is File Manager? It is a program module, which manages the allocation of space on disk storage and data structure used to represent information stored on a disk.
What is Authorization and Integrity manager? It is the program module, which tests for the satisfaction of integrity constraint and checks the authority of user to access data. What are stand-alone procedures? Procedures that are not part of a package are known as stand-alone because they independently defined. These types of procedures are not available for reference from other Oracle tools.
Another limitation of stand-alone procedures is that they are compiled at run time, which slows execution. What are cursors give different types of cursors. What is cold backup and hot backup in case of Oracle? This is a straight file copy, usually from the disk directly to tape. You must shut down the instance to guarantee a consistent copy. If a cold backup is performed, the only option available in the event of data file loss is restoring all the files from the latest backup.
All work performed on the database since the last backup is lost. The cold backup is not an available option. So different means of backing up database must be used — the hot backup. Issue a SQL command to indicate to Oracle, on a tablespace-by-tablespace basis, that the files of the tablespace are to backed up. The users can continue to make full use of the files, including making changes to the data. If a data loss failure does occur, the lost database files can be restored using the hot backup and the online and offline redo logs created since the backup was done.
The database is restored to the most consistent state without any loss of committed transactions. How can you find the minimal key of relational schema? Minimal key is one which can identify each tuple of the given relation schema uniquely.
For finding the minimal key it is required to find the closure that is the set of all attributes that are dependent on any given set of attributes under the given set of functional dependency. For each attribute A in K a.
What do you understand by dependency preservation? Given a relation R and a set of FDs F, dependency preservation states that the closure of the union of the projection of F on each decomposed relation Ri is equal to the closure of F.
What is meant by Proactive, Retroactive and Simultaneous Update. Proactive Update: The updates that are applied to database before it becomes effective in real world. Retroactive Update: The updates that are applied to database after it becomes effective in real world. Simultaneous Update: The updates that are applied to database at the same time when it becomes effective in real world.
What are the different types of JOIN operations? Equi Join: This is the most common type of join which involves only equality comparisons. The disadvantage in this type of join is that there Dept. What operator performs pattern matching? LIKE operator 3. What operator tests column for the absence of data? Which command executes the contents of a specified file? RUN 7. What are the wildcards used for pattern matching? State true or false. True 9. True What are the privileges that can be granted on a table by a user to others?
Insert, update, delete, select, references, index, execute, alter, all Which system tables contain information on privileges granted and privileges obtained? Which system table contains information on constraints on all the tables created?
What command is used to create a table by copying the structure of another table? What will be the output of the following query? What does the following query do? The null values in the commission column will be replaced by 0 and added to salary. Which date function is used to find the difference between two dates? Why does the following command give a compilation error? It is used to drop constraints specified on the table.
DESC has two purposes. It is used to describe a schema as well as to retrieve rows from table in descending order. When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
Which function is used to find the largest integer less than or equal to a specificvalue? FLOOR What is the output of the following query? Insert the given values into the tables: EMP: Dept. EMP; DEPT; List out all the privileges given to a particular user Delete records of ename column only and verify it Dept. EMPNO ; ROWID ; List all the information that this enterprise uses. Medical Clinic Database — The clinic has a number of regular patients and new patients come to the clinic regularly.
Patients make appointments to see one of the doctors; several doctors attend the clinic and they each have their own hours. Some doctors are General Practitioners GPs while others are specialists cardiologists, dermatologists etc. Patients have families and the family relationships are important. A medical record of each patient needs to be maintained. Information on prescriptions, insurance, allergies, etc needs to be maintained.
Different doctors may charge different fees. Billing has to be done for Patients. Academically, the university is divided into a number of faculties, such as Faculty of Engineering, Faculty of Architecture, Faculty of Management and Faculty of Science.
Some of the Faculties operate on a number of campuses. Faculties, in turn, are divided into schools; for example, the School of Architecture, the School of Information Technology. Each school is headed by a Director and has a number of teaching and non-teaching staff. Each school offers many courses. Each course consists of a fixed core of subjects and a number of electives from other courses. Each student in the University is enrolled in a single course of study. A subject is taught to the students Dept.
Chapter 1 - Introduction 2. Chapter 2 - Data Models. Chapter 4 - Database Constraints and Normalization 5. Chapter 5 - Query Processing and Optimization 6.
Chapter 7 - Transaction processing 8. Chapter 8 - Crash Recovery 9. Basic SQL Queries. Unknown 06 December. Anonymous 27 November. Popular posts from this blog Operating System - 24 April.
Syllabus 1. Chapter 1 - Introduction to Operating System 2. Chapter 2 - Process Management 3. Chapter 3 - Process Communication and Synchronization 4. Chapter 4 - Memory Management 5. Chapter 5 - File Systems 6. Chapter 7 - Deadlock 8.
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