tag:blogger.com,1999:blog-43490633810724286102024-02-08T08:39:27.591-08:00Mohan's OracleDBA Interview QuestionsOracleDBA Interview QuestionsUnknownnoreply@blogger.comBlogger57125tag:blogger.com,1999:blog-4349063381072428610.post-2581890220960476342013-07-23T12:17:00.001-07:002013-07-23T12:17:14.058-07:00What is data block ?<div class=Section1> <p class=MsoNormal>Oracle database's data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-6572390886498124722013-07-23T12:16:00.005-07:002013-07-23T12:16:57.158-07:00What is network database link ?<div class=Section1> <p class=MsoNormal>Network database link is created and managed by a network domain service. A network database link can be used when any user of any database in the network specifies a global object name in a SQL statement or object definition.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-35400017885985009882013-07-23T12:16:00.003-07:002013-07-23T12:16:37.690-07:00What is public database link ?<div class=Section1> <p class=MsoNormal>Public database link is created for the special user group PUBLIC. A public database link can be used when any user in the associated database specifies a global object name in a SQL statement or object definition.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-13667831978600959222013-07-23T12:16:00.001-07:002013-07-23T12:16:22.271-07:00What is private database link ?<div class=Section1> <p class=MsoNormal>Private database link is created on behalf of a specific user. A private database link can be used only when the owner of the link specifies a global object name in a SQL statement or in the definition of the owner's views or procedures.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-76767271615637327922013-07-23T12:15:00.006-07:002013-07-23T12:16:04.092-07:00What are the types of database links ?<div class=Section1> <p class=MsoNormal>Private database link, public database link & network database link.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-45485317164634853022013-07-23T12:15:00.005-07:002013-07-23T12:15:48.005-07:00What is database link ?<div class=Section1> <p class=MsoNormal>A database link is a named object that describes a "path" from one database to another.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-21793150185347017032013-07-23T12:15:00.003-07:002013-07-23T12:15:31.640-07:00When can hash cluster used ?<div class=Section1> <p class=MsoNormal>Hash clusters are better choice when a table is often queried with equality queries. For such queries the specified cluster key value is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-40453430547720739892013-07-23T12:15:00.001-07:002013-07-23T12:15:14.749-07:00What is hash cluster ?<div class=Section1> <p class=MsoNormal>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.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-4834807695537595632013-07-23T12:13:00.001-07:002013-07-23T12:13:16.314-07:00What is index cluster ?<div class=Section1> <p class=MsoNormal>A cluster with an index on the cluster key.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-87168385985174909732013-07-23T12:12:00.005-07:002013-07-23T12:12:58.980-07:00What is cluster key ?<div class=Section1> <p class=MsoNormal>The related columns of the tables in a cluster are called the cluster key.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-3077340460468174102013-07-23T12:12:00.003-07:002013-07-23T12:12:38.280-07:00What are clusters ?<div class=Section1> <p class=MsoNormal>Clusters are groups of one or more tables physically stores together to share common columns and are often used together.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-59250842822094530402013-07-23T12:12:00.001-07:002013-07-23T12:12:21.219-07:00How are the index updates ?<div class=Section1> <p class=MsoNormal>Indexes are automatically maintained and used by Oracle. Changes to table data are automatically incorporated into all relevant indexes.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-62465508062919675422013-07-23T12:11:00.001-07:002013-07-23T12:11:50.932-07:00What is an Oracle index ?<div class=Section1> <p class=MsoNormal>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.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-56996565903760732692013-07-23T11:57:00.006-07:002013-07-23T11:58:04.696-07:00What are synonyms used for ?<div class=Section1> <p class=MsoNormal>Mask the real name and owner of an object.<o:p></o:p></p> <p class=MsoNormal>Provide public access to an object<o:p></o:p></p> <p class=MsoNormal>Provide location transparency for tables, views or program units of a remote database.<o:p></o:p></p> <p class=MsoNormal>Simplify the SQL statements for database users.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-78081060171548949142013-07-23T11:57:00.005-07:002013-07-23T11:57:44.287-07:00What is a public synonym ?<div class=Section1> <p class=MsoNormal>Any database user can access a public synonym.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-40845235522146185192013-07-23T11:57:00.003-07:002013-07-23T11:57:22.072-07:00What is a private synonym ?<div class=Section1> <p class=MsoNormal>Only its owner can access a private synonym.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-21489123303496142522013-07-23T11:57:00.001-07:002013-07-23T11:57:15.326-07:00What are the types of synonyms ?<div class=Section1> <p class=MsoNormal>There are two types of synonyms private and public.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-88000766366519629432013-07-23T11:56:00.007-07:002013-07-23T11:56:59.014-07:00What is a synonym ?<div class=Section1> <p class=MsoNormal>A synonym is an alias for a table, view, sequence or program unit.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-90234419693327320922013-07-23T11:56:00.005-07:002013-07-23T11:56:45.620-07:00What is an Oracle sequence ?<div class=Section1> <p class=MsoNormal>A sequence generates a serial list of unique numbers for numerical columns of a database's tables.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-30566224613291740852013-07-23T11:56:00.003-07:002013-07-23T11:56:30.756-07:00What are the advantages of views ?<div class=Section1> <p class=MsoNormal>Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.<o:p></o:p></p> <p class=MsoNormal>Hide data complexity.<o:p></o:p></p> <p class=MsoNormal>Simplify commands for the user.<o:p></o:p></p> <p class=MsoNormal>Present the data in a different perspective from that of the base table.<o:p></o:p></p> <p class=MsoNormal>Store complex queries.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-70411959109487639152013-07-23T11:56:00.001-07:002013-07-23T11:56:10.376-07:00Do a view contain data ?<div class=Section1> <p class=MsoNormal>Views do not contain or store data.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-14598737008487902222013-07-23T11:55:00.005-07:002013-07-23T11:55:55.187-07:00What is an Oracle view ?<div class=Section1> <p class=MsoNormal>A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-19784072485066732692013-07-23T11:55:00.003-07:002013-07-23T11:55:40.092-07:00What is Oracle table ?<div class=Section1> <p class=MsoNormal>A table is the basic unit of data storage in an Oracle database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-23579293374762651392013-07-23T11:55:00.001-07:002013-07-23T11:55:21.659-07:00What are Schema Objects ?<div class=Section1> <p class=MsoNormal>Schema objects are the logical structures that directly refer to the database's data. Schema objects include tables, views, sequences, synonyms, indexes, clusters, database triggers, procedures, functions packages and database links.<o:p></o:p></p> </div> Unknownnoreply@blogger.comtag:blogger.com,1999:blog-4349063381072428610.post-2268927000294265502013-07-23T11:53:00.005-07:002013-07-23T11:53:49.375-07:00What is schema?<div class=Section1> <p class=MsoNormal>A schema is collection of database objects of a user.<o:p></o:p></p> </div> Unknownnoreply@blogger.com