Top 100+ Oracle Core Dba Interview Questions And Answers
Question 1. What Is Consistent Backup?
Answer :
A Consistent backup is one wherein the documents being backed up contain all changes upto the same gadget exchange wide variety (SCN).
Question 2. What Is Fractured Block?
Answer :
Because the database keeps writing to the document for the duration of a web backup, there's the possibility of backing up inconsistent facts within a block. For instance, count on that either RMAN or an running system application reads the block whilst database author is within the center of updating the block. In this example, RMAN or the replica utility may want to examine the antique records within the pinnacle half of of the block and the new statistics inside the bottom pinnacle half of of the block. The block is a fractured block, that means that the facts in this block isn't regular.
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Question 3. What Are The Steps To Performing Complete Recovery On The Whole Database?
Answer :
Mount the database
Ensure that each one datafiles you want to get better are on-line
Restore a backup of the whole database or the documents you need to get better
Apply online or archived redo logs, or a combination of the two
Question four. What Are The Steps To Performing Complete Recovery On A Tablespace Or Datafile?
Answer :
Take the tablespace or datafile to be recovered offline if the database is open.
Restore a backup of the datafiles you want to get better.
Apply online or archived redo logs, or a mixture of the two.
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Question five. What Are The Components Of Physical Database Structure Of Oracle Database?
Answer :
Oracle database is comprised of three styles of documents. One or more datafiles, are greater redo log files, and one or extra manage documents.
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Question 6. What Are The Components Of Logical Database Structure Of Oracle Database?
Answer :
There are tablespaces and database's schema items.
Question 7. What Is A Tablespace?
Answer :
A database is split into Logical Storage Unit known as tablespaces. A tablespace is used to grouped associated logical structures together.
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Question eight. What Is System Tablespace And When Is It Created?
Answer :
Every Oracle database includes a tablespace named SYSTEM, that's automatically created while the database is created. The SYSTEM tablespace continually contains the information dictionary tables for the whole database.
Question nine. Explain The Relationship Among Database, Tablespace And Data File?
Answer :
Each databases logically divided into one or more tablespaces one or extra information documents are explicitly created for each tablespace.
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Question 10. What Is Schema?
Answer :
A schema is series of database items of a consumer.
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Question eleven. What Are Schema Objects?
Answer :
Schema gadgets are the logical systems that without delay consult with the database's statistics. Schema items consist of tables, views, sequences, synonyms, indexes, clusters, database triggers, techniques, functions packages and database hyperlinks.
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Question 12. Can Objects Of The Same Schema Reside In Different Tablespaces?
Answer :
Yes.
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Question thirteen. Can A Tablespace Hold Objects From Different Schemes?
Answer :
Yes
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Question 14. What Is Oracle Table?
Answer :
A desk is the fundamental unit of records storage in an Oracle database. The tables of a database maintain all the person reachable information. Table facts is stored in rows and columns.
Question 15. What Is An Oracle View?
Answer :
A view is a digital desk. Every view has a question connected to it. (The query is a SELECT declaration that identifies the columns and rows of the table(s) the view uses.)
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Question sixteen. Do A View Contain Data?
Answer :
Views do no longer incorporate or save records.
Question 17. Can A View Based On Another View?
Answer :
Yes.
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Question 18. What Are The Advantages Of Views?
Answer :
Provide a further level of table protection, via restricting get admission to to a predetermined set of rows and columns of a table.
Hide information complexity.
Simplify instructions for the consumer.
Present the facts in a special angle from that of the base desk.
Store complicated queries.
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Question 19. What Is An Oracle Sequence?
Answer :
A collection generates a serial list of particular numbers for numerical columns of a database's tables.
Question 20. What Is A Synonym?
Answer :
A synonym is an alias for a table, view, series or application unit.
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Question 21. What Are The Types Of Synonyms?
Answer :
There are styles of synonyms non-public and public.
Question 22. What Is A Private Synonym?
Answer :
Only its owner can get entry to a private synonym.
Question 23. What Are Synonyms Used For?
Answer :
Mask the real name and proprietor of an item. - Provide public get right of entry to to an object - Provide area transparency for tables, views or application devices of a far off database. - Simplify the SQL statements for database customers.
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Question 24. What Is An Oracle Index?
Answer :
An index is an optional shape associated with a table to have direct get admission to to rows, which can be created to increase the performance of records retrieval. Index may be created on one or greater columns of a desk.
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Question 25. How Are The Index Updated?
Answer :
Indexes are mechanically maintained and utilized by Oracle. Changes to table records are robotically integrated into all applicable indexes.
Question 26. What Are Clusters?
Answer :
Clusters are businesses of 1 or extra tables bodily shops together to proportion not unusual columns and are frequently used collectively.
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Question 27. What Is Cluster Key?
Answer :
The associated columns of the tables in a cluster are referred to as the cluster key.
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Question 28. What Is Index Cluster?
Answer :
A cluster with an index on the cluster key.
Question 29. What Is Hash Cluster?
Answer :
A row is stored in a hash cluster based on the end result of applying a hash characteristic to the row's cluster key cost. All rows with the equal hash key value are stores together on disk.
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Question 30. When Can Hash Cluster Used?
Answer :
Hash clusters are higher preference whilst a table is regularly queried with equality queries. For such queries the desired cluster key fee is hashed. The resulting hash key price factors at once to the vicinity on disk that stores the desired rows.
Question 31. What Is Database Link?
Answer :
A database hyperlink is a named item that describes a "route" from one database to some other.
Question 32. What Are The Types Of Database Links?
Answer :
Private database link, public database link & community database hyperlink.
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Question 33. What Is Private Database Link?
Answer :
Private database hyperlink is created on behalf of a specific consumer. A private database hyperlink can be used handiest while the owner of the hyperlink specifies a global item name in a SQL assertion or within the definition of the owner's views or tactics.
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Question 34. What Is Public Database Link?
Answer :
Public database link is created for the special user group PUBLIC. A public database hyperlink can be used while any person in the related database specifies a global item name in a SQL announcement or item definition.
Question 35. What Is Network Database Link?
Answer :
Network database hyperlink is created and managed by way of a network area service. A network database hyperlink can be used when any user of any database inside the community specifies a global item name in a SQL declaration or object definition.
Question 36. What Is Data Block?
Answer :
Oracle database's records is saved in facts blocks. One statistics block corresponds to a selected wide variety of bytes of physical database space on disk.
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Question 37. How To Define Data Block Size?
Answer :
A information block length is distinctive for every Oracle database when the database is created. A database users and allocated loose database area in Oracle information blocks. Block size is laid out in init.Ora file and can't be modified latter.
Question 38. What Is Row Chaining?
Answer :
In situations, all of the data for a row in a desk won't be capable of suit within the equal data block. When this happens, the records for the row is saved in a chain of facts block (one or extra) reserved for that section.
Question 39. What Is An Extent?
Answer :
An quantity is a particular variety of contiguous facts blocks, obtained in a unmarried allocation and used to store a specific kind of information.
Question 40. What Is A Segment?
Answer :
A section is a fixed of extents allotted for a certain logical shape.
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Question 41. What Are The Different Types Of Segments?
Answer :
Data segment, index section, rollback phase and temporary segment.
Question 42. What Is A Data Segment?
Answer :
Each non-clustered table has a statistics phase. All of the table's facts is stored within the extents of its statistics segment. Each cluster has a statistics section. The information of every table inside the cluster is stored in the cluster's statistics segment.
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Question forty three. What Is An Index Segment?
Answer :
Each index has an index section that stores all of its records.
Question forty four. What Is Rollback Segment?
Answer :
A database carries one or greater rollback segments to temporarily shop "undo" statistics.
Question 45. What Are The Uses Of Rollback Segment?
Answer :
To generate study-steady database facts all through database recovery and to rollback uncommitted transactions through the users.
Question 46. What Is A Temporary Segment?
Answer :
Temporary segments are created by means of Oracle whilst a SQL assertion desires a temporary paintings vicinity to complete execution. When the announcement finishes execution, the transient section extents are launched to the system for future use.
Question forty seven. What Is A Datafile?
Answer :
Every Oracle database has one or more physical records documents. A database's facts documents contain all of the database data. The facts of logical database structures which include tablesand indexes is physically stored inside the information files allotted for a database.
Question 48. What Are The Characteristics Of Data Files?
Answer :
A records record can be associated with handiest one database. Once created a information report can't alternate size. One or extra data documents form a logical unit of database garage referred to as a tablespace.
Question forty nine. What Is A Redo Log?
Answer :
The set of redo log files for a database is collectively called the database redo log.
Question 50. What Is The Function Of Redo Log?
Answer :
The primary function of the redo log is to file all modifications made to statistics.
Question fifty one. What Is The Use Of Redo Log Information?
Answer :
The statistics in a redo log document is used simplest to recover the database from a gadget or media failure prevents database facts from being written to a database's statistics documents.
Question 52. What Does A Control File Contains?
Answer :
Database name - Names and places of a database's files and redolog files. - Time stamp of database introduction.
Question 53. What Is The Use Of Control File?
Answer :
When an instance of an Oracle database is started, its manipulate record is used to pick out the database and redo log files that have to be opened for database operation to proceed. It is likewise utilized in database recuperation.
