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Oracle Data Guard Interview Questions
Q1) Why do you think using Data Guard by Oracle is helpful to our work?
Ans: The benefits of using the software are many in any environment dealing with data. It ensures that the data stays protected and easily available. You get to take the load off from backups to the standby operations database. The problems like gaps in the standby database are automatically detected and resolved. The guard broker allows automated role transition.
Q2) Name the three top services offered by the Data Guard software?
Ans: The three top services offered by the software are:
1. Redoing the transport service
2. Applying for log service
3. Role transitional services
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Q3) Name the three protection modes available in the software.
Ans: The three protection modes that are available include maximum availability, protection, and performance.
Q4) What is the default protection mode of the software?
Ans: The default mode in the software Data Guard is Maximum performance.
Q5) What are the advantages offered by the Maximum Performance protection mode?
Ans: The main advantage of this default mode is that the performance of the primary data is not affected while the highest possible level of protection for the data is ensured. The transactions begin to commit as soon as the redone data produced by the transactions get written on to the online log.
Q6) What are the benefits of maximum protection mode?
Ans: This protection mode comes to the rescue when the primary database fails. The primary database shuts down and stops processing the transaction when this protection mode is enabled. So with this protection mode, you can be assured that there will be no data loss.
Q7) How is the maximum protection mode enabled?
Ans: The redone data must get written in two places before committing the transaction- the online log and a standby database. This way the primary database can shut down but the data remains intact.
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Q8) What are the advantages of maximum availability protection mode?
Ans: The biggest advantage with one is that the availability of the primary database is uncompromised but the maximum possible level of protection is offered to the data. The transactions with this protection mode only commit when all the redone data needed to recover the transactions get written to a standby database and the online log.
Q9) How is the protection mode changed?
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Ans: The steps for changing the protection mode are as follows:
1. Go to the alter database option.
2. Set the standby database.
3. Select from the three available options of performance, availability, and protection
Q10) What is the number of standby databases that can be created?
Ans: It depends on what version of the software is at your disposal. The general number ranges from nine to thirty standby databases.
Q11) How would you create a physical Standby in this software?
Ans: The following easy steps can create a physical standby in the software:
- Enabling of the forced logging
- Creating a password file
- Configuration of a standby redone log
- The archiving is enabled
- Setting up of the parameters for initialization of the primary database
- Configure the needful settings that support the database of both the nodes.
Q12) Mention the chief advantages of using Physical database standby in the software.
Ans: There is a fourfold advantage to using the physical database standby.
1. The higher availability quotient
2. The high capability of balancing the load including both reporting as well as backup.
3. Protecting the data
4. Recovery of data in the case of disasters
Q13) What services are needed on the primary database?
Ans: Four basic services are required on the primary database. They are as follows:
1. The Log Writer: Updates the online redone logs by collecting the information. It creates localized archived logs and causes the transmission of the redo ones to the standby bases.
2. The Archive Process: Copying of the online redone logs for the standby bases in a remote or localized manner.
3. The Fetch Archive Log: Servicing of the request for archived logs from the Fetch Archive Log customers that run on more than one standby basis. More than one server can run on the primary database where for each Fetch Archive Log request, there is one server.
4. Log Network: It gets used on the primary database to establish a connection with that of standby.
Q14) Outline the services needed on the standby database.
Ans: There are four services required on standby:
1. Fetch Archive Log: The archived redo files get pulled from primary sites. The transfer of the archived redo files is initiated on the detection of a sequence gap.
2. Remote File: The Primary database is used to receive the archived or standby redone logs. You can get both the archived and the standby logs together as well.
3. Archive Process: The standby redone logs that get applied by managed recovery are archived by this service.
4. Managed Recovery: The archived redo log details are applied to the standby databank.
Q15) How would you delay an application of the logs to the physical standby mode?
Ans: The standby gets naturally applied to the redo logs at the time of their arrival from the primary database. There are times when a time lag is needed to be created between archiving a redo log at the primary point and applying the log at standby.
You need to modify the parameter for initialization on the primary site to lead to a delay on the standby site. For instance, if you want a delay of one hour, you can set the log for delay at sixty minutes. It is worth mentioning in this regard that the delay is always given in minutes in the format of, for instance, 60′.
With this action, the redo logs are still copied from the primary to the standby site but it does not immediately apply. They get applied after the expiry of the specific time interval that has been set.
Q16) What is the utility of the Redo Transport Service?
Ans: It is used for controlling the automatic transmission of redo data of the production database in one or multiple archives. The following tasks are successfully performed by it:
1. Transmission of redo data from primary to standby in the configuring.
2. The management of the process of handling gaps in archive log files initiated as a result of the failure of the network.
3. Automatic detection of missing or corrupted archived log files in a standby database. It also automatically retrieves the replacement archived redone log from either the primary or standby system.
Q17) Differentiate between the standby database and the physical database.
Ans: The biggest difference between the two databases is the way of application of services to the archived redo files.
For the physical database, the software has a technology called Redo Apply. This one applies the redo on the standby system by the use of the basic recovery technique of the software. For the standard database, the software uses a technology called SQL. This one first transforms the redo it receives into statements and afterward the execution of the statements on the standby system is initiated.
Q18) What do you understand by Broker in this software?
Ans: The Broker helps in the management of standby and primary bases by the utilization of command-line, broker, or graphical interfaces. These are integrated into the Enterprise Manager software by Oracle.
Q19) What are the tasks that you can perform using the Broker?
Ans: It can be used to provide five benefits which have been listed below:
- Creating and enabling configurations for the software. This includes factors like the application and the transport redo services.
- Management of the complete configuration from any kind of system in the configuration.
- Monitoring and managing the configurations that have the standby or the primary data.
- Simplification of failover and switchover by letting their invocation by using either one key click or by the use of a single command in the interface available in the software.
- On the unavailability of the primary data, the fast and start failover is enabled to failover naturally. When this failover gets enabled, the broker of the software determines the necessity of a failover. If it is deemed necessary, then it is initiated to the standby system naturally. There is no need for intervention from database applications.
Q20) What do you understand by Logical standby base in the software?
Ans: The logical database is created similar to the physical and standby database. The structure of the logical database can get altered at a later point in time. The sync with standby and the primary is made easy by the utilization of SQL. The received logs of redo are made into statements and they are continuously applied into logical databases. This way the standby system is made consistent with the primary. The report of purpose is made easier with logical standby as compared to the physical one. The logical database is available in both read-write modes. The tables that are in sync with primary data are made available in read-only operations only. So you get the availability on some queries, index adding, and reporting.
Q21) What are the disadvantages that are associated with the Logical Standby systems?
Ans: The only major disadvantage that this one has is in the matters of types of tables and a few of the data functions. On the overall aspects, it is held as having an advantage over the physical database.
Q22) Can this software get used with the standard edition released by the makers?
Ans: There are certain automated features that are not available in the standard edition. You can ship logs and write the scripts manually to get the steps done. On certain platforms, you get to write the scripts and then use the commands to ship it to the standby system. The recovery is then carried out manually and it is removed after the application is done.
Q23) What made you go for the training in this software?
Ans: The software is a huge advantage in the firms that require the handling of large amounts of data. The certification in this software helps to smoothen out the large data processes. You can save the corruption of data and provide ease of data recovery. The trained professional becomes an inevitable asset to the company whenever it goes through any kind of data emergency. The basic yet complicated job of data backup and processing is made easy by the use of the software. The trained professional in this software is an important troubleshooter for the company which is what gives a person a professional advantage in the current scenario.
Q24) What do you understand by apply services in this software?
Ans: The apply services refer to the application of the redo data on the standby system to keep the transactional sync with the primary system. This redo data can get applied from either archived redo files or from the standby redo files directly as they get filled. The application from the standby redo files is only possible if the real-time facility gets enabled. It does not require the redo log to get archived at the standby system first. One of the main features of this service is that it also permits read-only accessibility to the data.