Advanced DBA RAC Interview Questions and Answers- webbopedia

Here we have mentioned most frequently asked DBA/RAC Interview Questions and Answers specially for freshers and experienced.

1. Where are the Clusterware files stored on a RAC environment?

Ans:

The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file)

2. Where are the database software files stored on a RAC environment?

Ans:

The base software is installed on each node of the cluster and the database storage on the shared disks.

3. What kind of storage we can use for the shared Clusterware files?

Ans:

OCFS (Release 1 or 2)
raw devices
third party cluster file system such as GPFS or Veritas

4. What kind of storage we can use for the RAC database storage?

Ans:

OCFS (Release 1 or 2)
ASM
raw devices
third party cluster file system such as GPFS or Veritas

5. What is a CFS?

Ans:

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.

6. What is an OCFS2?

Ans:

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

7. Which files can be placed on an Oracle Cluster File System?

Ans:

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.

8. Do you know another Cluster Vendor?

Ans:

HP Tru64 Unix, Veritas, Microsoft

9. How is possible to install a RAC if we don’t have a CFS?

Ans:

This is possible by using a raw device.

10. What is a raw device?

Ans:

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.

11. What is a raw partition?

Ans:

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.

12. When to use CFS over raw?

Ans:

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.

13. When to use raw over CFS?

Ans:

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.

14. What CRS is?

Ans:

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.

15. What is VIP IP used for?

Ans:

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.

16. Why we need to have configured SSH or RSH on the RAC nodes?

Ans:

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.

17. Is the SSH, RSH needed for normal RAC operations?

Ans:

No. SSH or RSH are needed only for RAC, patch set installation and clustered database creation.

18. Do we have to have Oracle RDBMS on all nodes?

Ans:

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).

19. What are the restrictions on the SID with a RAC database? Is it limited to 5 characters?

Ans:

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.

20. Does Real Application Clusters support heterogeneous platforms?

Ans:

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

21. Are there any issues for the interconnect when sharing the same switch as the public network by using VLAN to separate the network?

Ans:

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.

22. What is the Load Balancing Advisory?

Ans:

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.

23. How many nodes are supported in a RAC Database?

Ans:

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.

24. What is the Cluster Verification Utiltiy (cluvfy)?

Ans:

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.

25. What versions of the database can I use the cluster verification utility (cluvfy) with?

Ans:

The cluster verification utility is release with Oracle Database 10g Release 2 but can also be used with Oracle Database 10g Release 1.

26. If I am using Vendor Clusterware such as Veritas, IBM, Sun or HP, do I still need Oracle Clusterware to run Oracle RAC 10g?

Ans:

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.

27. Is RAC on VMWare supported?

Ans:

Yes.

28. What is hangcheck timer used for ?

Ans:

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.

29. Is the hangcheck timer still needed with Oracle RAC 10g?

Ans:

Yes.

30. What files can I put on Linux OCFS2?

Ans:

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

31. Is it possible to use ASM for the OCR and voting disk?

Ans:

No, the OCR and voting disk must be on raw or CFS (cluster file system).

32. Can I change the name of my cluster after I have created it when I am using Oracle Clusterware?

Ans:

No, you must properly uninstall Oracle Clusterware and then re-install.

33. What the O2CB is?

Ans:

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

34. What the OCR file is used for?

Ans:

OCR is a file that manages the cluster and RAC configuration.

35. What the Voting Disk file is used for?

Ans:

The voting disk is nothing but a file that contains and manages information of all the node memberships.

36. What is the recommended method to make backups of a RAC environment?

Ans:

RMAN to make backups of the database, dd to backup your voting disk and hard copies of the OCR file.

37. What command would you use to check the availability of the RAC system?

Ans:

crs_stat -t -v (-t -v are optional)

38. What is the minimum number of instances you need to have in order to create a RAC?

Ans:

You can create a RAC with just one server.

39. Name two specific RAC background processes

Ans:

RAC processes are: LMON, LMDx, LMSn, LKCx and DIAG.

40. Can you have many database versions in the same RAC?

Ans:

Yes, but Clusterware version must be greater than the greater database version.

41. What was RAC previous name before it was called RAC?

Ans:

OPS: Oracle Parallel Server

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

Ans:

Private Interconnect.

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

Ans:

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

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

Ans:

srvctl

45. How many alert logs exist in a RAC environment?

Ans:

A- One for each instance.

46. What are Oracle Clusterware Components

Ans:

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

47. How do you backup voting disk

Ans:

#dd if=voting_disk_name of=backup_file_name

48. How do I identify the voting disk location

Ans:

#crsctl query css votedisk

49. How do I identify the OCR file location

Ans:

check /var/opt/oracle/ocr.loc or /etc/ocr.loc ( depends upon platform)
or
#ocrcheck

50. What is SCAN?

Ans:

Single Client Access Name (SCAN) is s a new Oracle Real Application Clusters (RAC) 11g Release 2 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.

51. Mention what is cluster?

Ans:

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

52. Mention what is Oracle Real Application Clusters?

Ans:

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.

53. Mention what are the main components of an Oracle RAC system?

Ans:

The main elements of an Oracle RAC system are,

Shared disk system
Oracle Clusterware
Cluster Interconnects
Oracle Kernel Components

54. Mention what are the benefits of Oracle RAC?

Ans:

Benefits of RAC is that

Business Continuity and High Availability
Workload Management with least expense
Agility and Scalability
System management and Standardized deployment

55. Mention what are the file storage options provided by Oracle Database for Oracle RAC?

Ans:

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

56. Mention what is the volume management techniques used in Oracle RAC?

Ans:

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.

57. Mention what is new feature in Oracle ASM 12c?

Ans:

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.

58. Mention how Oracle Flex ASM works?

Ans:

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.

59. Mention what are the key characteristics of RAC or why to use RAC?

Ans:

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

60. Mention what is the function of Cache Fusion in Oracle RAC?

Ans:

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.

61. Mention what is the difference between single instance environment and RAC environment?

Ans:

Single Instance Environment	RAC Environment
Instance has its own SGA (System Global Area)	Each instance has its own SGA
Datafiles and control files are accessed by only one instance	Datafiles and control files shared by all instances
Online redo logfile dedicated for read/write to only one instance	Online redo logfile only one instance can write, but other instances can read during recovery and archiving.
Flash recovery log accessed by only one instance	Flash recovery log shared by all instances
Alert log and trace files dedicated to the instance	Alert log and trace files are private to each instance. Other instance never write or read to those files

62. Mention what is split brain syndrome in RAC?

Ans:

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.

63. What happens if you keep split brain syndrome in RAC unresolved? How it can be resolved?

Ans:

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.

64. Mention how can you determine what protocol is being used for Interconnect traffic?

Ans:

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.

65. Mention in RAC what files should be created on shared storage?

Ans:

In RAC ControlFiles, Spfiles, Redolog files, and Datafiles should be created on shared storage.

66. Mention where does the Clusterware write when there is a network or storage issue?

Ans:

When there is a network or storage issue the network ping failure is written in $CRS_HOME/log

67. Mention what are the tools provided in Oracle Enterprise Manager?

Ans:

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.

68. Mention what is the difference between Instance recovery and Crash recovery?

Ans:

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.

69. What if your OCR (Oracle Cluster Registry) is corrupted?

Ans:

if your OCR is corrupted, you can either use the logical or physical OCR backup copy to restore the repository.

70. Mention what is OLR?

Ans:

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.

71. What is cache fusion?

Ans:

In a RAC environment, it is the combining of data blocks, which are shipped across the interconnect from remote database caches (SGA) to the local node, in order to fulfill the requirements for a transaction (DML, Query of Data Dictionary).

72. What is split brain?

Ans:

When database nodes in a cluster are unable to communicate with each other, they may continue to process and modify the data blocks independently. If the
same block is modified by more than one instance, synchronization/locking of the data blocks does not take place and blocks may be overwritten by others in the cluster. This state is called split brain.

73. What is the difference between Crash recovery and Instance recovery?

Ans:

When an instance crashes in a single node database on startup a crash recovery takes place. In a RAC enviornment the same recovery for an instance is performed by the surviving nodes called Instance recovery.

74. What is the interconnect used for?

Ans:

It is a private network which is used to ship data blocks from one instance to another for cache fusion. The physical data blocks as well as data dictionary blocks are shared across this interconnect.

75. How do you determine what protocol is being used for Interconnect traffic?

Ans:

One of the ways is to look at the database alert log for the time period when the database was started up.

76. What methods are available to keep the time synchronized on all nodes in the cluster?

Ans:

Either the Network Time Protocol(NTP) can be configured or in 11gr2, Cluster Time Synchronization Service (CTSS) can be used.

77. What files components in RAC must reside on shared storage?

Ans:

Spfiles, ControlFiles, Datafiles and Redolog files should be created on shared storage.

78. Where does the Clusterware write when there is a network or Storage missed heartbeat?

Ans:

The network ping failure is written in $CRS_HOME/log

79. How do you find out what OCR backups are available?

Ans:

The ocrconfig -showbackup can be run to find out the automatic and manually run backups.

80. If your OCR is corrupted what options do have to resolve this?

Ans:

You can use either the logical or the physical OCR backup copy to restore the Repository.

81. How do you find out what object has its blocks being shipped across the instance the most?

Ans:

You can use the dba_hist_seg_stats.

82. What is a VIP in RAC use for?

Ans:

The VIP is an alternate Virtual IP address assigned to each node in a cluster. During a node failure the VIP of the failed node moves to the surviving node and relays to the application that the node has gone down. Without VIP, the application will wait for TCP timeout and then find out that the session is no longer live due to the failure.

83. How do we know which database instances are part of a RAC cluster?

Ans:

You can query the V$ACTIVE_INSTANCES view to determine the member instances of the RAC cluster.

84. What is OCLUMON used for in a cluster environment?

Ans:

The Cluster Health Monitor (CHM) stores operating system metrics in the CHM repository for all nodes in a RAC cluster. It stores information on CPU, memory, process, network and other OS data, This information can later be retrieved and used to troubleshoot and identify any cluster related issues. It is a default component of the 11gr2 grid install. The data is stored in the master repository and replicated to a standby repository on a different node.

85. What would be the possible performance impact in a cluster if a less powerful node (e.g. slower CPU’s) is added to the cluster?

Ans:

All processing will show down to the CPU speed of the slowest server.

86. What is the purpose of OLR?

Ans:

Oracle Local repository contains information that allows the cluster processes to be started up with the OCR being in the ASM storage ssytem. Since the ASM file system is unavailable until the Grid processes are started up a local copy of the contents of the OCR is required which is stored in the OLR.

87. What is the default memory allocation for ASM?

Ans:

In 10g the default SGA size is 1G in 11g it is set to 256M and in 12c ASM it is set back to 1G.

88. How do you backup ASM Metadata?

Ans:

You can use md_backup to restore the ASM diskgroup configuration in-case of ASM diskgroup storage loss.

89. What files can be stored in the ASM diskgroup?

Ans:

In 11g the following files can be stored in ASM diskgroups.
1. Datafiles
2. Redo logfiles
3. Spfiles
In 12c the files below can also new be stored in the ASM Diskgroup
1. Password file

90. What it the ASM POWER_LIMIT?

Ans:

This is the parameter which controls the number of Allocation units the ASM instance will try to rebalance at any given time. In ASM versions less than 11.2.0.3 the default value is 11 however it has been changed to unlimited in later versions.

91. What is a rolling upgrade?

Ans:

A patch is considered a rolling if it is can be applied to the cluster binaries without having to shutting down the database in a RAC environment. All nodes in the cluster are patched in a rolling manner, one by one, with only the node which is being patched unavailable while all other instance open.

92. What are some of the RAC specific parameters?

Ans:

Some of the RAC parameters are:
1. CLUSTER_DATABASE
2. CLUSTER_DATABASE_INSTANCE
3. INSTANCE_TYPE (RDBMS or ASM)
4. ACTIVE_INSTANCE_COUNT
5. UNDO_MANAGEMENT

93. What is the future of the Oracle Grid?

Ans:

The Grid software is becoming more and more capable of not just supporting HA for Oracle Databases but also other applications including Oracle’s applications. With 12c there are more features and functionality built-in and it is easier to deploy these pre-built solutions, available for common Oracle applications.

94. What are the components required to manage Oracle Real Application Clusters Database?

Ans:

Oracle RAC uses a single system in the form of an image to configure and manage the servers in an easy way. It provides a database for the installed and configured applications from one location so that it can be managed in an easy way.
The components required to be provided with it is as follows:

Oracle Universal Installer (OUI) is used to manage the database that is related to the cluster and provide enterprise level configuration.
Database configuration assistant (DBCA) that manages the database and its related functionality and services.
Database upgrade assistant (DBUA) is the tool that allows the database to be upgraded when it is required on the server.

95. Why is Cluster Verification Utility so important in Oracle RAC?

Ans:

Cluster Verification Utility is a tool in the Oracle Grid that is used to eliminate the errors that come up with the validations of the steps.
It provides the verification on the changes that is being made in the configuration of the files or the system.
The tool can be used with the command line interface and it is used to validate the configuration input as well such that during the installation it can be found out that everything is perfectly ok.
The tool is used to verify the system pre-requisites that are related to Oracle Clusterware, ASM and the databases.
There are few fix up scripts available if by any means the verification tool fails then these scripts can be used to automatically fix the errors.

96. What components of the Grid should I back up?

Ans:

The backups should include OLR, OCR and ASM Metadata.

97. Is there an easy way to verify the inventory for all remote nodes

Ans:

You can run the OPATCH LSINVENTORY -ALL_NODES command from a single node to look at the inventory details for all nodes in the cluster.

98. What is cache fusion?

Ans:

99. What is split brain?

Ans:

When database nodes in a cluster are unable to communicate with each other, they may continue to process and modify the data blocks independently. If the same block is modified by more than one instance, synchronization/locking of the data blocks does not take place and blocks may be overwritten by others in the cluster. This state is called split brain.

100. What is the difference between Crash recovery and Instance recovery?

Ans:

101. What is the interconnect used for?

Ans:

102. How do you determine what protocol is being used for Interconnect traffic?

Ans:

One of the ways is to look at the database alert log for the time period when the database was started up.

103. What methods are available to keep the time synchronized on all nodes in the cluster?

Ans:

Either the Network Time Protocol(NTP) can be configured or in 11gr2, Cluster Time Synchronization Service (CTSS) can be used.

104. What files components in RAC must reside on shared storage?

Ans:

Spfiles, ControlFiles, Datafiles and Redolog files should be created on shared storage.

105. Where does the Clusterware write when there is a network or Storage missed heartbeat?

Ans:

The network ping failure is written in $CRS_HOME/log

106. How do you find out what OCR backups are available?

Ans:

The ocrconfig -showbackup can be run to find out the automatic and manually run backups.

107. If your OCR is corrupted what options do have to resolve this?

Ans:

You can use either the logical or the physical OCR backup copy to restore the Repository.

108. How do you find out what object has its blocks being shipped across the instance the most?

Ans:

You can use the dba_hist_seg_stats.

109. What is a VIP in RAC use for?

Ans:

110. How do we know which database instances are part of a RAC cluster?

Ans:

You can query the V$ACTIVE_INSTANCES view to determine the member instances of the RAC cluster.

111. What is OCLUMON used for in a cluster environment?

Ans:

112. What would be the possible performance impact in a cluster if a less powerful node (e.g. slower CPU’s) is added to the cluster?

Ans:

All processing will show down to the CPU speed of the slowest server.

113. What is the purpose of OLR?

Ans:

114. What is the default memory allocation for ASM?

Ans:

In 10g the default SGA size is 1G in 11g it is set to 256M and in 12c ASM it is set back to 1G.

115. How do you backup ASM Metadata?

Ans:

You can use md_backup to restore the ASM diskgroup configuration in-case of ASM diskgroup storage loss.

116. What files can be stored in the ASM diskgroup?

Ans:

In 11g the following files can be stored in ASM diskgroups.

Datafiles
Redo logfiles
Spfiles
In 12c the files below can also new be stored in the ASM Diskgroup
Password file

117. What it the ASM POWER_LIMIT?

Ans:

118. What is a rolling upgrade?

Ans:

119. What are some of the RAC specific parameters?

Ans:

Some of the RAC parameters are:

CLUSTER_DATABASE
CLUSTER_DATABASE_INSTANCE
INSTANCE_TYPE (RDBMS or ASM)
ACTIVE_INSTANCE_COUNT
UNDO_MANAGEMENT

120. What is the future of the Oracle Grid?

Ans:

121. What components of the Grid should I back up?

Ans:

The backups should include OLR, OCR and ASM Metadata.
Is there an easy way to verify the inventory for all remote nodes
You can run the opatch lsinventory -all_nodes command from a single node to look at the inventory details for all nodes in the cluster.

122. Describe the Oracle Real Application Clusters Architecture?

Ans:

Oracle RAC consists of a database that is represented in a clustered manner in the architecture. The cluster is the collection or pool of independent servers that make up one single system.
Cluster architecture provides more flexibility to manage and follow a modular incremental approach to improve the fault errors and provide an incremental system.
This architecture provides the maximum security in terms of ensuring high availability of the resources to the users.
It provides the resources on demand and provides hardware architecture such as failure at a single point is being removed.
The architecture provides the decoupling of the Oracle instance like the process and memory that are running on the server from the Oracle database.

123. What was the main purpose of Oracle Real Application Clusters (RAC)?

Ans:

Oracle Real Application (RAC) provides the interaction of executable file with the Oracle database.
It allows the running of any packaged or custom built application with Oracle DB that is running on a server pool.It provides very high level of availability, flexibility and scalability to run the application and store it to the database.
It creates the database such that if the pool fails then the database is continued to run from the remaining servers and the load can be distributed.It makes it easier for the administrator to maintain many servers at the same time by load-balancing techniques and providing provision to add more and more servers when the load increases.

124. Differentiate Crash recovery and Instance recovery?

Ans:

When an instance crashes in a single node database on startup a crash recovery takes place. In a RAC environment the same recovery for an instance is performed by the surviving nodes called Instance recovery.

125. What is the interconnect used for?

Ans:

A private N/W which is used to ship data blocks from one instance to another for cache fusion. The physical data blocks as well as data dictionary blocks are shared across this interconnect.

126. How do you determine what protocol is being used for Interconnect traffic?

Ans:

One of the ways is to look at the DB alert log for the time period when the DB was started up.

127. What methods are available to keep the time synchronized on all nodes in the cluster?

Ans:

Either the Network Time Protocol(NTP) can be configured or in 11gr2, Cluster Time Synchronization Service (CTSS) can be used.

128. What files components in RAC must reside on shared storage?

Ans:

Spfiles, ControlFiles, Datafiles and Redolog files should be created.

129. How do you find out what OCR backups are available?

Ans:

The ocrconfig -showbackup can be run to find out the automatic and manually run backups.

130. If your OCR is corrupted what options do have to resolve this?

Ans:

You can use either the logical or the physical OCR backup copy to restore the Repository.

131. How do you find out what object has its blocks being shipped across the instance the most?

Ans:

You can use the dba_hist_seg_stats.

132. What is a VIP in RAC use for?

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133. How do we know which database instances are part of a RAC cluster?

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You can query the V$ACTIVE_INSTANCES view to determine the member instances of the RAC cluster.

134. What is OCLUMON used for in a cluster environment?

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135. What would be the possible performance impact in a cluster if a less powerful node (e.g. slower CPU’s) is added to the cluster?

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All processing will show down to the CPU speed of the slowest server.

136. How do you backup ASM Metadata?

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You can use md_backup to restore the ASM diskgroup configuration in-case of ASM diskgroup storage loss.

137. What files can be stored in the ASM diskgroup?

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In 11g the following files can be stored in ASM diskgroups.

Datafiles
Redo logfiles
Spfiles

In 12c the files below can also new be stored in the ASM Diskgroup

Password file

138. What it the ASM POWER_LIMIT?

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139. What is a rolling upgrade?

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140. What are some of the RAC specific parameters?

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Some of the RAC parameters are:

CLUSTER_DATABASE
CLUSTER_DATABASE_INSTANCE
INSTANCE_TYPE (RDBMS or ASM)
ACTIVE_INSTANCE_COUNT
UNDO_MANAGEMENT

141. What is the future of the Oracle Grid?

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142. Is there an easy way to verify the inventory for all remote nodes?

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You can run the opatch lsinventory -all_nodes command from a single node to look at the inventory details for all nodes in the cluster.

143. What is cache fusion?

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144. What is split brain?

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When database nodes in a cluster are unable to communicate with each other, they may continue to process and modify the data blocks independently. If the same block is modified by more than one instance, synchronization/locking of the data blocks does not take place and blocks may be overwritten by others in the cluster. This state is called split brain.

145. What is the Load Balancing Advisory?

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Load balancing advisory is a process through which the load of the applications and resources can be managed throughout the servers.
It monitors the workload of the current activities from all the clusters and the instances that is being given on the server.
The service that is being provided is active all the time to see the workload of the applications on the servers.
To simplify it, it provides a percentage value to show the total workload of the instance and it flags the instance according to the quality.
Load Balancing Advisory helps in maintaining the loads from the servers and equally distributes it among many other servers that are not currently working.

146. What is the default memory allocation for ASM?

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In 10g the default SGA size is 1G in 11g it is set to 256M and in 12c ASM it is set back to 1G.

147. What components of the Grid should I back up?

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The backups should include OLR, OCR and ASM Metadata.