Interview Questions.

Data Guard Interview Questions and Answers


Data Guard Interview Questions and Answers

Q1. What is supposed via Data Guard?

Ans: The software which Oracle Corporation markets as Oracle Data Guard forms an extension to the Oracle relational database management machine (RDBMS). It aids in organising and preserving secondary standby databases as opportunity/supplementary repositories to production primary databases.

Oracle provides both graphical consumer interface (GUI) and command-line (CLI) gear for coping with Data Guard configurations.

Data Guard helps each physical standby and logical standby websites. Oracle Corporation makes Data Guard available handiest as a bundled feature protected inside its "Enterprise Edition" of the Oracle RDBMS.[1]

With accurately set-up Data Guard operations, DBAs can facilitate failovers or switchovers to opportunity hosts within the identical or alternative places.

Q2. What are the styles of Oracle Data Guard?

Ans: Oracle Data Guard classified in to 2 kinds primarily based on way of advent and method used for Redo Apply. They are as follows.

Physical standby(Redo Apply technology)

Logical standby(SQL Apply Technology)

Snapshot standby(no longer applied until the photo standby is Converted)

Q3. What is using standby redolog?

Ans: The Advantage of having Standby Redo Logs is that every statistics written into the Online RedoLogs of the Primary Database

is transferred to the Standby database and written into the Standby Redo Logs at the equal time.

Therefore, you it minimizes the probability of Data Loss at the Standby Database.

For actual time apply, it's miles obligatory to have redolog.

Without Standby Redo Logs, an Archived Redo Log is created by means of the RFS method and whilst it has finished,

this Archived Redo Log is implemented to the Standby Database by the MRP process . An incomplete ArchiveLog file can not be implemented on the Standby Database and could not be utilized in a Failover situation. This reasons a positive statistics loss.

If you have got Standby Redo Logs, the RFS system will write into the Standby Redo Log ,while there file entered in online redolog and whilst a log switch occurs, the Archiver Process of the Standby Database will archive this Standby Redo Log to an Archived Redo Log, even as the MRP technique applies the data to the Standby Database. In a Failover scenario, you may additionally have access to the records already written inside the Standby Redo Logs, so the facts will no longer be lost.

Q4. What are the advantages in using Oracle Data Guard?

Ans: Following are the specific advantages in the usage of Oracle Data Guard feature on your surroundings:

High Availability.

Data Protection.

Off loading Backup operation to standby database.

Automatic Gap detection and Resolution in standby database.

Automatic Role Transition the use of Data Guard Broker.

Q5. What is lively dataguard. Does it needs additional licensing?

Ans: Active dataguard manner, the standby database is open with read best mode;

while redo logs are getting implemented in real time.

Below are the advantage of the use of lively dataguard:

Reporting queries may be offloaded to standby database.

Physical block corruptions are repaired robotically both at number one or bodily standby database.

RMAN backups can be initiated from standby , alternatively  of number one which will lessen cpu load from number one.

NOTE: To use active dataguard, you want extra license from oracle.

Q6. What are the specific offerings available in Oracle Data Guard?

Ans: Following are the exceptional Services available in Oracle Data Guard of Oracle database:

Redo Transport Services.

Log Apply Services.

Role Transitions.

Redo Transport Services

Control the automatic transfer of redo records from the manufacturing database to at least one or greater archival locations.

Apply Services

Apply redo facts on the standby database to keep transactional synchronization with the primary database. Redo records can be carried out either from archived redo log files, or, if actual-time observe is enabled, without delay from the standby redo log files as they're being crammed, with out requiring the redo facts to be archived first on the standby database.

Role Transitions:

Change the role of a database from a standby database to a primary database, or from a number one database to a standby database the usage of either a switchover or a failover operation.

Q7. What are the distinct kinds of redo shipping offerings in dataguard?

Ans: SYNC and ASYNC.


This mode is used for optimum protection and most availability protection mode. The synchronous redo delivery mode transmits redo data synchronously with appreciate to transaction dedication. A transaction can't dedicate till all redo generated via that transaction has been successfully sent to each standby locations.


This mode is used for max performance mode. A transaction can devote with out anticipating the redo generated by means of that transaction to be successfully sent to any redo transport vacation spot that makes use of the asynchronous redo delivery mode.

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Q8. What are the special Protection modes available in Oracle Data Guard?

Ans: Following are the exclusive safety modes to be had in Data Guard of Oracle database you can use anyone based totally in your application requirement.

Maximum Protection

Maximum Availability

Maximum Performance (Default Mode)

Q9. What are the brand new function for DG in 11g?

Ans: Active database replica

photo stand by means of

Active information guard

Redo compression

32 standby database  configuration guide (earlier most effective 9)

FAL_CLIENT not require

Q10. How to test what safety mode of primary database for your Oracle Data Guard?

Ans: By the use of following question you could take a look at safety mode of number one database to your Oracle Data Guard setup:

SQL> pick protection_mode from v$database;




Q11. What is distinction between Real time observe and redo observe?

Ans: In actual time observe, LOG APPLY Service will no longer watch for the modern SRL to archive .SO the redo information is practice AS SOON AS it acquire from primary.

But in normal follow mode : LOG APPLY carrier will watch for SRL to archive.

Q12. How to exchange protection mode in Oracle Data Guard setup?

Ans: By using following query your can trade the protection mode for your number one database after putting in place required fee in corresponding LOG_ARCHIVE_DEST_n parameter in primary database for corresponding standby database.

Q13. Which process is answerable for Redo log information  transmitting?

Ans: LGWR or ARCH.

Q14. What are the benefits of the usage of Physical standby database in Oracle Data Guard?

Ans: Advantages of the use of Physical standby database in Oracle Data Guard are as follows:

High Availability.

Load balancing (Backup and Reporting).

Data Protection.

Disaster Recovery.

Q15. Which parameter consumer for GAP Resolution?


When MRP reveals that an archive log is lacking all through media restoration, it sends the fal_client data to the server recognized by means of fal_server and requests fal_server to resend the document again.  The fal_client and fal_server init.Ora (spfile) parameters are set on the standby example

Q16. What is physical standby database in Oracle Data Guard?

Ans: Provides a bodily equal replica of the primary database, with on disk database structures which might be same to the primary database on a block-for-block foundation. The database schema, inclusive of indexes, are the same. A physical standby database is saved synchronized with the number one database, through Redo Apply, which recovers the redo facts acquired from the primary database and applies the redo to the physical standby database.

As of Oracle Database 11g release 1 (eleven.1), a bodily standby database can obtain and observe redo whilst it is open for read-simplest access. A physical standby database can consequently be used concurrently for facts safety and reporting.

Q17. What is distinction among Physical stand by and photo standby?

Ans: Snapshot stdb will obtain redo however not follow .Normal standby will receive and follow redo.

Q18. What is Logical standby database in Oracle Data Guard?

Ans: Contains the equal logical statistics because the manufacturing database, even though the physical organization and structure of the information can be exclusive. The logical standby database is saved synchronized with the number one database through SQL Apply, which transforms the statistics within the redo acquired from the primary database into SQL statements after which executes the SQL statements at the standby database.

A logical standby database may be used for other business functions similarly to disaster recuperation requirements. This permits customers to access a logical standby database for queries and reporting functions at any time. Also, the usage of a logical standby database, you can improve Oracle Database software and patch sets with almost no downtime. Thus, a logical standby database may be used concurrently for data safety, reporting, and database enhancements.

Q19. What is energetic dataguard  duplicate?

Ans: Starting from 11g we can replica database by using two way:

Active DB reproduction.

Backup-based replica.

Active DB reproduction copies the live TARGET DB over the community to the AUXILLARY vacation spot after which create the reproduction database.In an energetic duplication process, target database online image copies and archived redo log documents had been copied thru the auxiliary example service call. So there's no want of target db backup.

Q20. What is Snapshot standby database in Oracle Data Guard?

Ans: A snapshot standby database is a completely updatable standby database. Like a bodily or logical standby database, a photo standby database receives and data redo facts from a number one database. Unlike a bodily or logical standby database, a image standby database does now not follow the redo statistics that it receives. The redo information obtained via a photograph standby database isn't applied till the photo standby is transformed back into a bodily standby database, after first discarding any local updates made to the photograph standby database.

A picture standby database is satisfactory used in scenarios that require a transient, updatable photo of a bodily standby database. Note that because redo statistics received via a photograph standby database isn't always applied until it's far transformed back right into a bodily standby, the time needed to recover from a number one database failure is at once proportional to the amount of redo data that desires to be applied.