Interview

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1.What is SCAN?
Single Client Access Name (SCAN) is s a new Oracle Real Application Clusters (RAC) 11g Release feature that provides a single name for clients to access an Oracle Database running in a cluster. The
benefit is clients using SCAN do not need to change if you add or remove nodes in the cluster.

2. What is cluster?
A cluster is referred to a group of independent, but connected servers that behaves as a single system.

3. What is Oracle Real Application Clusters?
RAC or Real Application Cluster is a component of the database product that enables the database to
be installed across multiple servers. Oracle RAC uses Oracle Clusterware for the infrastructure to
bind multiple servers, so they operate as a single system.

4. What are the main components of an Oracle RAC system?
The main elements of an Oracle RAC system are,
 Shared disk system
 Oracle Clusterware
 Cluster Interconnects
 Oracle Kernel Components

5. What are the benefits of Oracle RAC?
Benefits of RAC is that,
 Business Continuity and High Availability
 Workload Management with least expense
 Agility and Scalability
 System management and Standardized deployment

6. What are the file storage options provided by Oracle Database for Oracle RAC?
The file storage options provided by Oracle Database for Oracle RAC are,
 Automatic Storage Management (ASM)
 OCFS2 and Oracle Cluster File System (OCFS)
 A network file system
 Raw devices

7. What is the volume management techniques used in Oracle RAC?
Volume management techniques used in Oracle RAC is that,
 Oracle RAC provides dynamic volume manager. It has a file system that consists of
information of the cluster file system.
 Cluster file system in Oracle is known as OCFS. It has the connection with the databases that
provide raw devices and command line features.

8. What is new feature in Oracle ASM 12c?
The new feature added in Oracle ASM 12c is Oracle Flex ASM. Its a new ASM deployment model
which increases instance database availability and reduces the Oracle ASM related resource
consumption.

9. How Oracle Flex ASM works?
Oracle Flex ASM instance when fails on a particular node, then the Oracle Flex ASM instance is
passed over to another node in the cluster.

10. What are the key characteristics of RAC or why to use RAC?
The key characteristics of RAC are,
 Reliability: Eliminates the database server from a single point of failure. If an instance fails,
the remaining instances in the cluster remain active and open.
 Error Detection: Provides fast detection of problems in the environment. It automatically
recovers from failures even before user’s notice that a failure has occurred.
 Recoverability: Easy to recover from various types of failures.
 Continuous Operations: provides continuous service for both unplanned and planned
outages.

11. What is the function of Cache Fusion in Oracle RAC?
Cache function is used to show the storage of the information in the clustered network with the Oracle
database. It involves two nodes, one writes the data to the same disk, and other reads the data block
from the disk. For its network connection, RAC uses a dedicated server for its network, and cache
function is an internal part of the cluster.

12. What is CRS?
Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent
set of system services for cluster environments. In Release 2, Oracle has renamed this product to
Oracle Clusterware.

13. What is VIP IP used for?
It returns a dead connection IMMIDIATELY, when its primary node fails. Without using VIP IP, the
clients have to wait around 10 minutes to receive ORA-3113: “end of file on communications
channel”. However, using Transparent Application Failover (TAF) could avoid ORA-3113.

14. How can you determine what protocol is being used for Interconnect traffic?
To determine what protocol is being used for Interconnect traffic you can look at the database alert
log for the time period when the database was started up.

15. In RAC what files should be created on shared storage?
In RAC Controlfiles, Spfiles, Redolog files, and Datafiles should be created on shared storage.

16. What is the difference between Instance recovery and Crash recovery?
A crash recovery takes place when an instance crashes in a single node database on startup. When the
same recovery for an instance is performed in RAC environment by the surviving nodes then it is
called Instance recovery.

17. What if your OCR (Oracle Cluster Registry) is corrupted?
If your OCR is corrupted, you can either use the logical or physical OCR backup copy to restore the
repository.

18. What is OLR?
ORL stands for Oracle Local Repository (OLR). It consists of information which enables the cluster
programs to initiate with the OCR in the ASM Storage. Until the grid process are started, the ASM
file is unavailable. In such case, a local copy of the data of the OCR is required, that is stored in
OLR.

19. Where are the Clusterware files stored on a RAC environment?
The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting
disks and the CSR file)

20. Where are the database software files stored on a RAC environment?
The base software is installed on each node of the cluster and the database storage on the shared
disks.

21. What is a CFS?
A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in
a cluster at the same time. This implies that all members of a cluster have the same view.

22. What is an OCFS2?
The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real
Application Cluster.

23. Where does the Clusterware write when there is a network or storage issue?
When there is a network or storage issue the network ping failure is written in $CRS_HOME/log

24. What are the tools provided in Oracle Enterprise Manager?
Tools provided in Oracle Enterprise Manager are,
Grid Control-
 It is used to deliver the centralized management system and provides configuration and
administration capabilities.
 It provides the cost reduction plans and provides higher efficiency
Database Control-
 It is used as a graphical management tool to manage the database to make it configure
automatically.
 It is related to the Oracle Clusterware. It is used to maintain the services of the Oracle RAC.
 It also manages the server pools that are being created with the Oracle Clusterware and provision
to manage it from a single place.

25. What are 12c ASM Enhancements?
 Flex ASM simple you do not need 4 ASM instances for 4 nodes, 3 is enough as like scan.
 ASM metadata is now copied to multiple allocation units in the disk header.
 Replace disk command.
 Now you can create 511 diskgroups no more 64 limit.
 Now you can estimate the rebalance/resync operations.
 12c stores password files in ASM.
 Check logical corruptions using disk scrubbing.
 Failuregroup_repair_time for whole group in contrast to diskgroup_repair_time.
 OCR backup now goes to ASM disk group.

26. Grid Infrastructure enhancements.
 Flex Cluster – HUB and Leaf spoke technology, just to ensure to couple the application layer
and database layer closely.
 IPV6 Support – You can have ipv6 format and ipv4 format network attachments to cluster.
 Convert normal cluster to flex cluster.
 crsctl commands in eval mode.

27. RAC enhancements.
 Application continuity – Transaction Guard – New API to protect the transactions state and
reapply them in case service failure.
 New failover_type = transaction when using application continuity.
 Global data services.
 srvctl evaluation mode

28. Security Features.
 wide range of auditing is enabled and all auditing details will be stored initially in memory
tables and then flushed to unified_audit_trail.
 Unified auditing is a consolidated audit for database where all operations like rman
backup/restores, expdp/impdp, general audits, fga will be collected and stored in
unified_audit trail table instead of sys.aud$ table and this new table is placed sysaux
tablespace.
 dbms_privilege_capture procedure gives you the ability to monitor the privilege usage.
 Resource role does not contain the unlimited tablespace now.
 select any dictionary privilege does not access the some sensitive tables like default_pwd$
tables.

29. What kind of storage we can use for the shared Clusterware files?
 CFS (Release 1 or 2)
 raw devices
 third party cluster file system such as GPFS or Veritas

30. What kind of storage we can use for the RAC database storage?
 OCFS (Release 1 or 2)
 ASM
 raw devices
 third party cluster file system such as GPFS or Veritas.

31. What is split brain syndrome in RAC?
In Oracle RAC, all the instances/servers communicate with each other using a private network. When
the instance members in a RAC fail to ping/connect to each other via this private network and
continue to process data block independently. Then this process is referred as Split Brain Syndrome.

32. What happens if you keep split brain syndrome in RAC unresolved? How it can be resolved?
If you keep split brain syndrome unresolved, then there would be data integrity issue. The blocks
changed in one instance will not be locked and could be over-written by another instance. It is
resolved by using the voting disk, it will decide which node(s) will survive and which node(s) will be
evicted.

33. Which files can be placed on an Oracle Cluster File System?
 Oracle Software installation (Windows only)
 Oracle files (controlfiles, datafiles, redologs, files described by the bfile datatype)
 Shared configuration files (spfile)
 OCR and voting disk
 Files created by Oracle during runtime
 Note: There are some platform specific limitations.

34. Do you know another Cluster Vendor?
HP Tru64 Unix, Veritas, Microsoft

35. How is possible to install a RAC if we don’t have a CFS?
This is possible by using a raw device.

36. What is a raw device?
A raw device is a disk drive that does not yet have a file system set up. Raw devices are used for Real
Application Clusters since they enable the sharing of disks.

37. What is a raw partition?
A raw partition is a portion of a physical disk that is accessed at the lowest possible level. A raw
partition is created when an extended partition is created and logical partitions are assigned to it
without any formatting. Once formatting is complete, it is called cooked partition.

38. When to use CFS over raw?
A CFS offers:
 Simpler management
 Use of Oracle Managed Files with RAC
 Single Oracle Software installation
 Autoextend enabled on Oracle datafiles
 Uniform accessibility to archive logs in case of physical node failure
 With Oracle_Home on CFS, when you apply Oracle patches CFS guarantees that the updated
Oracle_Home is visible to all nodes in the cluster.
 Note: This option is very dependent on the availability of a CFS on your platform.

39. When to use raw over CFS?
 Always when CFS is not available or not supported by Oracle.
 The performance is very, very important: Raw devices offer best performance without any
intermediate layer between Oracle and the disk.
 Note: Autoextend fails on raw devices if the space is exhausted. However the space could be
added online if needed.

40. Why we need to have configured SSH or RSH on the RAC nodes?
SSH (Secure Shell,10g+) or RSH (Remote Shell, 9i+) allows “oracle” UNIX account connecting to
another RAC node and copy/ run commands as the local “oracle” UNIX account.

41. Is the SSH, RSH needed for normal RAC operations?
No. SSH or RSH are needed only for RAC, patch set installation and clustered database creation.

42. Do we have to have Oracle RDBMS on all nodes?
Each node of a cluster that is being used for a clustered database will typically have the RDBMS and
RAC software loaded on it, but not actual data files (these need to be available via shared disk).

43. What are the restrictions on the SID with a RAC database? Is it limited to 5 characters?
The SID prefix in 10g Release 1 and prior versions was restricted to five characters by install/ config
tools so that an ORACLE_SID of up to max of 5+3=8 characters can be supported in a RAC
environment. The SID prefix is relaxed up to 8 characters in 10g Release 2, see bug 4024251 for
more information.

44. Does Real Application Clusters support heterogeneous platforms?
The Real Application Clusters do not support heterogeneous platforms in the same cluster.

45. Are there any issues for the interconnect when sharing the same switch as the public network
by using VLAN to separate the network?
RAC and Clusterware deployment best practices suggests that the interconnect (private connection)
be deployed on a stand-alone, physically separate, dedicated switch. On big network the connections
could be instable.

46. What is the Load Balancing Advisory?
To assist in the balancing of application workload across designated resources, Oracle Database 10g
Release 2 provides the Load Balancing Advisory. This Advisory monitors the current workload
activity across the cluster and for each instance where a service is active; it provides a percentage
value of how much of the total workload should be sent to this instance as well as service quality flag.

47. How many nodes are supported in a RAC Database?
With 10g Release 2, we support 100 nodes in a cluster using Oracle Clusterware, and 100 instances in
a RAC database. Currently DBCA has a bug where it will not go beyond 63 instances. There is also a
documentation bug for the max-instances parameter. With 10g Release 1 the Maximum is 63.

48. What is the Cluster Verification Utiltiy (cluvfy)?
The Cluster Verification Utility (CVU) is a validation tool that you can use to check all the important
components that need to be verified at different stages of deployment in a RAC environment.

49. What versions of the database can I use the cluster verification utility (cluvfy) with?
The cluster verification utility is release with Oracle Database 10g Release 2 but can also be used
with Oracle Database 10g Release 1.

50. If I am using Vendor Clusterware such as Veritas, IBM, Sun or HP, do I still need Oracle
Clusterware to run Oracle RAC 10g?
Yes. When certified, you can use Vendor Clusterware however you must still install and use Oracle
Clusterware for RAC. Best Practice is to leave Oracle Clusterware to manage RAC. For details see
Metalink Note 332257.1 and for Veritas SFRAC see 397460.1.

51. Is RAC on VMWare supported?
Yes.

52. What is hangcheck timer used for ?
The hangcheck timer checks regularly the health of the system. If the system hangs or stop the node
will be restarted automatically.
There are 2 key parameters for this module:
 hangcheck-tick: this parameter defines the period of time between checks of system health.
The default value is 60 seconds; Oracle recommends setting it to 30seconds.
 hangcheck-margin: this defines the maximum hang delay that should be tolerated before
hangcheck-timer resets the RAC node.

53. What files can I put on Linux OCFS2?
For optimal performance, you should only put the following files on Linux OCFS2:
 Datafiles
 Control Files
 Redo Logs
 Archive Logs
 Shared Configuration File (OCR)
 Voting File

 SPFILE
54. Is it possible to use ASM for the OCR and voting disk?
No, the OCR and voting disk must be on raw or CFS (cluster file system).
55. Can I change the name of my cluster after I have created it when I am using Oracle
Clusterware?
No, you must properly uninstall Oracle Clusterware and then re-install.

56. What the O2CB is?
The O2CB is the OCFS2 cluster stack. OCFS2 includes some services. These services must be started
before using OCFS2 (mount/ format the file systems).

57. What the OCR file is used for?
OCR is a file that manages the cluster and RAC configuration.

58. What the Voting Disk file is used for?
The voting disk is nothing but a file that contains and manages information of all the node
memberships.

59. What command would you use to check the availability of the RAC system?
crs_stat -t -v (-t -v are optional)

60. What is the minimum number of instances you need to have in order to create a RAC?
You can create a RAC with just one server.

61. Name two specific RAC background processes?
RAC processes are: LMON, LMDx, LMSn, LKCx and DIAG.

62. Can you have many database versions in the same RAC?
Yes, but Clusterware version must be greater than the greater database version.

63. What was RAC previous name before it was called RAC?
OPS: Oracle Parallel Server.

64. What RAC component is used for communication between instances?

65. Private Interconnect.

66. What is the difference between normal views and RAC views?

67. A RAC view has the prefix ‘G’. For example, GV$SESSION instead of V$SESSION.

68. Which command will we use to manage (stop, start) RAC services in command-line mode?
Srvctl.

69. How many alert logs exist in a RAC environment?
One for each instance.

70. What are Oracle Clusterware Components?
 Voting Disk - Oracle RAC uses the voting disk to manage cluster membership by way of a
health check and arbitrates cluster ownership among the instances in case of network failures.
The voting disk must reside on shared disk.
 Oracle Cluster Registry (OCR) - Maintains cluster configuration information as well as
configuration information about any cluster database within the cluster. The OCR must reside
on shared disk that is accessible by all of the nodes in your cluster.

71. How do you backup voting disk?
dd if=voting_disk_name of=backup_file_name.

72. How do I identify the voting disk location?
crsctl query css votedisk

73. How do I identify the OCR file location?
check /var/opt/oracle/ocr.loc or /etc/ocr.loc ( depends
1>DATA DISKGROUP IS RUNNING OUT OF SPACE,HOW WILL YOU CHECK IF THE DISK IS AVAILABLE IN THE GROUP OR ADD ANY DISK IN IT.

2>if no disk are available in asm.how will you increase space.

3>apart from asmcmd is ther any other way to check if any other disk are available or not.

4>what are the types of files we can keep in asm.

5>which files we cannot keep in asm

6>can you keep log files in asm ,alert and other log files.(ANS- IT IS AVAILABLE IN GRID HOME)

7>WHY DO WE NEED SEPERATE INSTANCE IN ASM.

8>WHAT IS YOUR RAC CONFIGURATIION.

9>What is the version of RAC.

10>was the rac on 12c since initial or was it earlier on 11g and upgraded to 12c.

11>which quater patch you appplied on rac.

12>steps for patch applied.

13>do you need to stop services before applying patch?

14>how will you stop the services on one node.solution(CRSCTL STOP HAS).will it stop the database also or you need to do it seperately.

15>how will you check the service.

16>once you do shut down which will be down first database or asm.

17>while starting up which one will come up first database or asm.

18>can you share the steps of stopping a rac.

19>how many database you have in your enviornment.

20>what is the scale of the enviornment you support.

21>what all versions are you working on currently in your enviornment.

22>are you supporting only linux enviornment.

23>what is the lowest version you have worked on.

24>explain each of the number in the version of a database say 11.2.0.1.14

25>if a tablespace has a datafile in a asm .Can you resize the tablespace.suppose a datafile in asm is 10GB .can you resize it to 20GB.
26>how to resize a tablespace in asm.

27>you have dataguard in your enviornment.is it physical or logical.

28>how will you check if database is in primary and is in sync or not.

29>if you have broker configured,how will you check if everything is in sync.

30>before making any changes to parameter file how will you check if it is dynamic or static one.

31>In RAC why do we have virtual IP in RAC.

32>suppose user raise a access request for particular database.and asked to provide the roles,priviledge & permisiions same as existing user user A.

33>How will extract the grand details of a user .

34>USER asked to restore a particular schema from production but also gave you a timestamp(suppose till yesterday 6 p:m).

35>where the rman backup piece is stored in your enviornment in local server or in netbackup.

36>what is retention period of RMAN backup.(ANS- 7 DAYS)So does it mean anything older than seven days u cannot restore.
37>do you have catalog  configured in your network.so does it means all the data are in control files.

38>IN DATAPUMP.Suppose u have seen log file is stuck in particular point for a very long time. ho w will u make sure that the import is happening properly. 

39>How can u dynamically monitor log file in linux.

40>which ticketing tool u use in your envionment.

41>do you have sla in your work.

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