Data Guard Interview Questions and Answers

1.  What are the different services available in Oracle Data Guard?

     Redo Transport Services.

Log Apply Services.

Role -Transitions.

2. What are the different Protection modes available in Oracle Data Guard?

Maximum Protection

Maximum Availability

Maximum Performance 

3. How to check what protection mode of primary database in your Oracle   Data Guard?

     SELECT PROTECTION_MODE FROM V$DATABASE;

4. How to change protection mode in Oracle Data Guard setup?

ALTER DATABASE SET STANDBY DATABASE TO MAXIMUM [PROTECTION|PERFORMANCE|AVAILABILITY];

5. What are the advantages of using Physical standby database in Oracle Data Guard?

High Availability.

Load balancing (Backup and Reporting).

Data Protection.

Disaster Recovery.


6. Reasons for Archivelog Gaps ?

1. Network issue :

       ping the standby server name from production you may got packet logs,if packet logs 50,70,100.... then may be a network issue ,then send a mail to network issue

$ping server name

2. Standby file system got full

            

3. Archive log got corrupted:

            we copy the same archivelog to primary and we start MRP process

7. What is the usage of DB_FILE_NAME_CONVERT parameter Oracle Data Guard setup?

DB_FILE_NAME_CONVERT parameter is used in Oracle Data Guard setup that to in standby databases. DB_FILE_NAME_CONVERT parameter are used to update the location of data files in standby database. These parameter are used when you are using different directory structure in standby database compare to primary database data files location.



8. What is the usage of LOG_FILE_NAME_CONVERT parameter in Oracle  Data Guard setup?


LOG_FILE_NAME_CONVERT parameter is used in Oracle Data Guard setup that to in standby databases. LOG_FILE_NAME_CONVERT parameter are used to update the location of redo log files in standby database. These parameter are used when you are using different directory structure in standby database compare to primary database redo log file location.

9. How many standby databases we can create (in 10g/11g)?

Till Oracle 10g, 9 standby databases are supported.

From Oracle 11g R2, we can create 30 standby databases.

10. What are differences between physical, logical, Snapshot Standby and ADG (or) what are different types of standbydatabases?

Physical Standby – in mount state, MRP will apply archives
ADG – in READ ONLY state, MRP will apply archives

Logical Standby – in READ ONLY state, LSP will run

Snapshot standby Database – Physical standby database can be converted to snapshot standby database, which will be in READ WRITE mode, can do any kind of testing, then we can convert back snapshot standby database to physical standby database and start MRP which will apply all pending archives

11. What are the parameters we’ve to set in primary/standby for Data Guard?

DB_UNIQUE_NAME

LOG_ARCHIVE_CONFIG

LOG_ARCHIVE_MAX_PROCESSES

DB_CREATE_FILE_DEST

DB_FILE_NAME_CONVERT

LOG_FILE_NAME_CONVERT

LOG_ARCHIVE_DEST_n

LOGARCHIVE_DEST_STATE_n

FAL_SERVER

FAL_CLIENT

STANDBY_FILE_MANAGEMENT

12. What is the use of fal_server & fal_client, is it mandatory to set these?

FAL SERVER

specifies the FAL (fetch archive log) server for a standby database. The value is an Oracle Net service name, which is assumed to be configured properly on the standby database system to point to the desired FAL server.

FAL CLIENT

specifies the FAL (fetch archive log) client name that is used by the FAL service, configured through the FAL_SERVER initialization parameter, to refer to the FAL client.The value is an Oracle Net service name, which is assumed to be configured properly on the FAL server system to point to the FAL client (standby database).

13. What is RTS (Redo Transport Services) in Dataguard?

It controls the automated transfer of redo data from the production database to one or more archival destinations. The redo transport services perform the following tasks:

a) Transmit redo data from the primary system to the standby systems in the configuration.
b) Manage the process of resolving any gaps in the archived redo log files due to a network failure.
c) Automatically detect missing or corrupted archived redo log files on a       standby system and automatically retrieve replacement archived redo log files   from the primary database or another standby database.

14. Switchover  Steps ?


a. identified what role the db plays

SQL> select database_role from v$database;



b. Initiate the switchover on the primary database

SQL> alter database commit to switchover to physical standby with session shutdown wait;



c. On the primary database shutdown and restart the instance.

SQL> shutdown immediate;

SQL> startup nomount;

SQL> alter database mount standby database;



d. Start the MRP process (Managed Recovery Process)

SQL> alter database recover managed standby database disconnect;



e.  Verify the switchover status in the v$database view. it should be SWITCHOVER PENDING status.

 SQL> select database_role from v$database;



f. Switch physical standby database role to the primary role.

SQL> alter database commit to switchover to primary with session shutdown wait;



g. Shutdown and restart the new primary database

SQL> shutdown

SQL> startup



h. Begin archiving logs to the physical standby database.

SQL> alter system archive log start;

SQL> alter system switch logfile;



15. FAILOVER Steps ?


a. Initiate the failover operation on the standby database

SQL> alter database recover managed standby database finish;



b. Convert the physical standby database to the primary role

SQL> alter database commit to switchover to primary;



c. Register the missing redo logs.

SQL> alter database register logfile '/standby/arch_dest/arch_1_101.arc';

                              Thank You