1. What do Database Buffers contain?
Database buffers store the most recently used blocks of database data. It can also contain modified data that has not yet been permanently written to disk.
2. What are the components of SGA?
Database buffers, Redo Log Buffer the Shared Pool and Cursors.
The System Global Area (SGA) is a shared memory region allocated by ORACLE that contains data and control information for one ORACLE instance.
4. What constitute an ORACLE Instance?
SGA and ORACLE background processes constitute an ORACLE instance. (or) Combination of memory structure and background process.
5. Explain an Integrity Constrains?
An integrity constraint is a declarative way to define a business rule for a column of a table.
The data dictionary of an ORACLE database is a set of tables and views that are used as a read-only reference about the database. It stores information about both the logical and physical structure of the database, the valid users of an ORACLE database, integrity constraints defined for tables in the database and space allocated for a schema object and how much of it is being used.
7. Explain the use of Control File?
When an instance of an ORACLE database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.
8. Explain What does a Control file Contain?
A Control file records the physical structure of the database. It contains the following information.
Database Name, Names and locations of a databases files and redolog files. ,Time stamp of database creation.
9. What is the use of Redo Log Information?
The Information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a databases data files.
10. What is the function of Redo Log?
The Primary function of the redo log is to record all changes made to data.
The set of Redo Log files for a database is collectively known as the databases redo log.
12. Explain What are the Characteristics of Data Files?
A data file can be associated with only one database.Once created a data file cant change size.
Every ORACLE database has one or more physical data files. A databases data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.
14. What is a Temporary Segment?
Temporary segments are created by ORACLE when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temporary segment extents are released to the system for future use.
15. Explain What are the uses of Rollback Segment?
Rollback Segments are used : To generate read-consistent database information during database recovery to rollback uncommitted transactions for users.
A Database contains one or more Rollback Segments to temporarily store "undo" information.
Each Index has an Index segment that stores all of its data.
Each Non-clustered table has a data segment. All of the tables data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is
19. Explain What are the different type of Segments?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
A segment is a set of extents allocated for a certain logical structure.
An Extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information.
In Circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs , the data for the row is stored in a chain of data block (one or more) reserved for that segment.
23. What is self-referential integrity constraint?
If a foreign key reference a parent key of the same table is called self-referential integrity constraint.
24. What are the Limitations of a CHECK Constraint?
The condition must be a Boolean expression evaluated using the values in the row being inserted or updated and can't contain subqueries, sequence, the SYSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.
A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.
A Cluster with an index on the Cluster Key.
The related columns of the tables in a cluster is called the Cluster Key.
29. Explain What are Clusters?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.
30. Explain How are Indexes Update?
Indexes are automatically maintained and used by ORACLE. Changes to table data are automatically incorporated into all relevant indexes.
An Index is an optional structure associated with a table to have direct access to rows,which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.
32. Explain What are synonyms used for?
Synonyms are used to :
Mask the real name and owner of an object. Provide public access to an object Provide location transparency for tables,views or program units of a remote database. Simplify the SQL statements for database users.
33. What is a Public Synonyms?
A Public synonyms can be accessed by any user on the database.
34. Explain a Private Synonyms?
A Private Synonyms can be accessed only by the owner.
35. Explain What are the type of Synonyms?
There are two types of Synonyms Private and Public.