Oracle Exadata Interview Questions and Answers

Oracle Exadata Interview Questions and Answers

Last updated on 16th Oct 2020, Blog, Interview Question

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If you’re looking for Oracle Exadata Interview Questions for Experienced or Freshers, you are at right place. There are lot of opportunities from many reputed companies in the world. According to research, Oracle Exadata has a market share of about 3.6%. So, You still have the opportunity to move ahead in your career in Oracle Exadata Development. ACTE offers Advanced Oracle Exadata Interview Questions 2021 that helps you in cracking your interview & acquire dream career as Oracle Exadata Developer.

1. What is Exadata?

Ans:

Exadata is a pre-configured combination of hardware and software which provides a platform to run the Oracle Database.

2. What environment is a good fit for Exadata?

Ans:

Exadata was originally designed for the warehouse environment. Later it was enhanced for use in the OLTP databases as well.

3. Key components of Exadata

Ans:

  • DB Server
  • Cell Storage
  • Infiniband Switch
  • Cisco Switch
  • PDU

4. Features of Exadata

Ans:

  • Smart Scan
  • Smart Flash Cache
  • IORM
  • Storage Index
  • EHCC (Exadata Hybrid Columnar Compression)

5. What are the advantages of Exadata?

Ans:

The Exadata cluster allows for consistent performance while allowing for increased throughput. As load increases on the cluster the performance remains consistent by utilizing inter-instance and intra-instance parallelism.

It should not be expected that just moving to Exadata will improve performance. In most cases it will especially if the current database host is overloaded.

6. What are the Exadata Sizing configurations?

Ans:

Exadata comes in following configuration

  • Full Rack
  • Half Rack
  • quarter Rack
  • 1/8th Rack

7. What is hybrid columnar compression?

Ans:

Hybrid Columnar compression, also called HCC, is a feature of Exadata which is used for compressing data at column level for a table.

It creates compression data units which consist of logical grouping of columns values typically having several data blocks in it. Each data block has data from columns for multiple rows.This logarithm has the potential to reduce the storage used by the data and reduce disk I/O enhancing performance for the queries.

The different types of HCC compression include:

  • very Low
  • very High
  • Archive High
  • Archive Low

8. What are the Parallelism instance parameters used in Exadata?

Ans:

The parameter PARALLEL_FORCE_LOCAL can be specified at the session level for a particular job.

9. How do you Test performance of Exadata?

Ans:

You can use the “calibrate” commands at the cellcli command line.

10. What are the ways to migrate onto Exadata?

Ans:

Depending on the downtime allowed there are several options:

  • Oracle DataGuard
  • Traditional Export/Import
  • Tablespace transportation
  • Goldengate Replication after a data restore onto Exadata.

11. What are the different Exadata configurations?

Ans:

The Exadata Appliance configuration comes as a Full Rack, Half Rack, quarter Rack or 1/8th rack. The Full Rack X2-2 has 6 CPUs per node with Intel Xeon 5670 processors and a total of 8 Database Server nodes. These servers have 96GB of memory on each node. A total of 14 Storage server cells communicate with the storage and push the requested data from the storage to the compute nodes.

The Half Rack has exactly half the capacity. It has 6 CPUs per node with core Intel Xeon 5670 processors and a total of 4 Database Server nodes. It has 96GB of memory per database server node with a total of 7 Storage server cells.

The Exadata is also available in the 1/8th Rack configuration.

12. What is the secret behind Exadata’s higher throughput?

Ans:

Exadata ships less data through the pipes between the storage and the database nodes and other nodes in the RAC cluster. Also its ability to do massive parallelism by running parallel processes across all the nodes in the cluster provides it a much higher level of throughput.

It also has much bigger pipes in the cluster using Infiniband interconnect for inter-instance data block transfers as high as 5X of fiber channel networks.

13. What is a storage index and how does it work?

Ans:

  • Storage Indexes consist of a minimum and a maximum value for up to eight columns. This structure is maintained for 1MB chunks of storage (storage regions).
  • Storage Indexes are stored in memory only and are never written to disk.
  • Storage Index filters out data from the consideration.
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14. Which protocol is used by ASR to send notification?

Ans:

SNMP

15. Is manually intervening possible in the storage index?

Ans:

No

16. What is cellcli?

Ans:

This is the command-line utility used to manage the cell storage.

17. How do you obtain info on the Cell Disks?

Ans:

At the cellcli command line you can issue the “list celldisk” command.

18. How would you create a grid disk?

Ans:

At the cellcli command you would need to issue the “create griddisk all ..” command.

19. What are the cellinit.ora and the cellip.ora files used for?

Ans:

These files have the IP address of all the nodes in the cluster. They are used to run commands on remote databases and cell server nodes from localhost.

Example:

  • cat /etc/oracle/cell/network-config/cellinit.ora
  • ipaddress1=192.168.47.21/24
  • $ cat /etc/oracle/cell/network-config/cellip.ora
  • cell=”192.168.47.21:5042″
  • cell=”192.168.47.22:5042″
  • cell=”192.168.47.23:5042″

20. What operating systems does Exadata support?

Ans:

Exadata has traditionally run Oracle Linux OS. Recently, Solaris has also been made available on this engineered system.

21. What are the options to update cell_flashcache for any object?

Ans:

  • KEEP
  • DEFAULT
  • NONE

22. What is the default size of smart flash log?

Ans:

  • 512MB per module.
  • Each storage cell having 4 modules so its 4X512 MB per CELL

23. What is flash cache and how it works?

Ans:

The flash cache is a hardware component configured in the exadata storage cell server which delivers high performance in read and write operations.

Primary task of smart flash cache is to hold frequently accessed data in flash cache so next time if same data required than physical read can be avoided by reading the data from flash cache.

24. Types of EHCC:

Ans:

  • very Low
  • very High
  • Archive High
  • Archive Low

25. Which package can be used to estimate the compression ratio of a table?

Ans:

DBMS_COMPRESSION

26. Background services of Cell Server

Ans:

  • MS- Management Server
  • cellsrv – Cell Server
  • RS – Restart Server

27.What is grid disk?

Ans:

Grid Disks are created on top of Cell Disks and are presented to Oracle ASM as ASM disks. 

Space is allocated in chunks from the outer tracks of the Cell disk and moving inwards. One can have multiple Grid Disks per Cell disk.

28. How to replace faulty HDD in Exadata Storage?

Ans:

All the HDD are hot swappable so if we are using proper redundancy then we can directly remove and replace the new HDD.

Storage software will take care of all the stuff in the background after replacing the HDD.

29. How many disks come within a storage cell?

Ans:

12

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30. What is the purpose of the spine switch?

Ans:

Spine switch is used to connect or add more Exadata machine in the cluster

31. How to migrate databases from normal setup to Exadata ?

Ans:

There are many methods we can use to migrate DB to Exadata. Below are some of them.

  • Export/Import
  • Physical Standby
  • Logical Standby
  • Transportable Tablespace
  • Transportable Database
  • Golden gate
  • RMAN cold and hot backup restoration
  • Oracle Streams

Use of migration method is totally depends on source setup as well as downtime consideration.””

32. Exadata shutdown and start-up procedure

Ans:

  • Shutdown Procedure:
  • Stop Database and Listener
  • Stop Cluster
  • Shutdown Database Servers
  • Shutdown Cell Storage
  • Shutdown all the switches
  • Remove powers from PDUs
  • Start-up procedure would be in reverse order.

33. How many database servers come in the 1/8th rack and quarter rack?

Ans:

2

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34. How much cell storage comes in a full rack exadata machine?

Ans:

14

35. Can we use flash disk as an ASM disk?

Ans:

Yes

36. Which protocol is used for communication between database server and storage server?

Ans:

iDB protocol

37. Which OS is supported in Exadata?

Ans:

Database servers have two options for OS either Linux or Solaris which can be finalized at the time of configuration Cell storage comes with Linux only.

38. What is ASR?

Ans:

ASR is the tool to manage the Oracle hardware. Full form of ASR is Auto Service Request. Whenever any hardware fault occurs ASR automatically raises SR in Oracle Support and sends notification to respective customers.

39. How to integrate Exadata with OEM 12c?

Ans:

  • Install OEM agent on DB server
  • Launch auto discovery with the use of One Command XML file
  • Specify required credentials for all the components
  • Review Configuration
  • Complete the setup

40. How to upgrade firmware of Exadata components?

Ans:

It can be done through ILOM of DB or Cell server.

41. Where can we define which cell storage can be used by a particular database server?

Ans:

CELLIP.ORA file contains the list of storage servers which are accessed by the DB server.

42. What are the Exadata Health check tools?

Ans:

  • Exachk
  • sundiagtest
  • oswatcher
  • OEM 12c

43. What is EHCC?

Ans:

EHCC is Exadata Hybrid Columnar Compression which is used to compress data in the Database.

44. What is offloading and how it works?

Ans:

It refers to the fact that part of the traditional SL processing done by the database can be “offloaded” from the database layer to the storage layer

The primary benefit of Offloading is the reduction in the volume of data that must be returned to the database server. This is one of the major bottlenecks of most  large databases.

45. What is the difference between cellcli and dcli?

Ans:

  • Cellcli can be used on respective cell storage only.
  • DCLi (Distributed command Line Utility) – DCLI can be used to replicate commands on multiple storage as well as DB servers.

46. What is IORM and what is its role in Exadata?

Ans:

IORM stands for I/O Resource Manager which manages the I/Os of multiple databases on a storage cell.

47. How can we check whether oracle best practice has been configured on Exadata?

Ans:

We can execute Exachk and verify the best practice setup on the Exadata machine.

48. How many networks required in Exadata?

Ans:

  • Public/Client Network — For Application Connectivity
  • Management Network — For Exadata H/W management
  • Private Network — For cluster inter connectivity and Storage connectivity

49. What is the command to enable query high compression on table?

Ans:

SL>alter table table_name move compress for query high;

50. How to take cell storage software backup?

Ans:

It is not required to take a backup as it happens automatically. Exadata uses an internal USB drive called the Cellboot Flash Drive to take backup of software.

51. What is the difference between write-through and write-back flashcache mode?

Ans:

  • write through –> Flash Cache will be used only for reading purpose
  • writeback –> Flashcache will be used for both reading and writing

52. Which feature of Exadata is used to eliminate disk IO?

Ans:

Flash Cache

53. What is the capacity of Infiniband port?

Ans:

40 Gbps

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54. What is the difference between high capacity and high performance disk?

Ans:

  • High capacity disk comes with more storage space and less rpm (7.5k)
  • High Performance disk comes with less storage and high rpm (15k)

55. When should one execute Exachk?

Ans:

Before and after any configuration change in Database Machine

56. Which network is used for RAC inter-connectivity?

Ans:

Infiniband Network

57. What are the steps to create DBFS?

Ans:

  • Create Directory
  • Create Tablespace on database which you are going to use for DBFS
  • Create user for DBFS
  • Grant required privileges to create user
  • Now connect to database with created user
  • Create dbfs filesystem by invoking dbfs_create_filesystem_advanced
  • Mount file system by starting dbfs_client

58. Which migration methodology is available if you want to migrate from high endian to low endian OS architecture?

Ans:

  • Golden Gate
  • Transportable Tablespace
  • Incremental Transportable Tablespace
  • Data Pump

59. What is a Cell and Grid Disk?

Ans:

Cell and Grid Disk are a logical component of the physical Exadata storage. A cell or Exadata Storage server cell is a combination of Disk Drives put together to store user data. Each Cell Disk corresponds to a LUN (Logical Unit) which has been formatted by the Exadata Storage Server Software. Typically, each cell has 12 disk drives mapped to it.

60. What is Flash cache?

Ans:

Four 96G PCIe flash memory cards are present on each Exadata Storage Server cell which provide very fast access to the data stored on it. This is further achieved by also providing a mechanism to reduce data access latency by retrieving data from memory rather than having to access data from disk. A total flash storage of 384GB per cell is available on the Exadata appliance.

61. What is Smart Scan?

Ans:

It is a feature of the Exadata Software which enhances the database performance many times over. It processes queries in an intelligent way, retrieving specific rows rather than the complete blocks. It applies filtering criteria at the storage level based on the selection criteria specified in the query. It also performs column projection which is a process of sending only required columns for the query back to the database host/instance.

62. Which statistic can be used to check flash hit ration on database level?

Ans:

Cell flash cache read hits

63. Which disk group is used to keep OCR files on Exadata?

Ans:

+DBFS_DG

64. How many Exadata wait events were contained in the 11.2.0.3 release?

Ans:

There are 53 wait events and specific events.

65. What is the difference between an Exadata X3-2 machine and an Exadata X3-8 machine?

Ans:

The X3-8 consists of 2 large SMP compute servers while the X3-2 can scale to as many as 8 compute servers as processing requirements increase.

66. What are the three major components of the Exadata database server?

Ans:

  • Database Instance
  • ASM Instance
  • Database Resource Manager

67. What is the difference between DBRM and IORM?

Ans:

DBRM is the feature of databases while IORM is the feature of storage server software.

68. What are the key Oracle Exadata Features?

Ans:

Some of the key hardware and software features are:

  • Hardware level
  • Storage Server Cells
  • High Speed Infiniband Switch
  • Software level
  • Smart Scan,
  • Flash Cache
  • . Hybrid Columnar Compression
  • IORM (I/O Resource Manager)

69. How much time is required to apply bundle patch on Half rack Exadata Database Machine with rolling option?

Ans:

Approximate 3 hours per Cell and DB server including Infiniband & PSU patching required 1 hour each

70. What benefit we can get if we apply bundle patch on exadata in rolling fashion while ASM configured with high redundancy?

Ans:

It will reduce the risk of storage disk failure

71. Advantages and disadvantages of rolling and non-rolling patching on Exadata Database Machine.

Ans:

Rolling

Advantages:

  • No downtime required

Disadvantages:

  • It takes more time to apply bundle patches
  • If ASM is on normal redundancy then disk failure on another Cell could lead to DB corruption.

Non-Rolling

Advantages:

  • Less time required to do the patching
  • It could eliminate the risk of single disk failure if ASM configured with normal redundancy

Disadvantages:

  • Downtime required while applying bundle patch.

72. Which ASM parameters are responsible for Auto disk management in Exadata?

Ans:

  • AUTO_MANAGE_MAX_ONLINE_TRIES — It controls maximum number of attempts to make disk Online
  • AUTO_MANAGE_EXADATA_DISKS — It control auto disk management feature
  • AUTO_MANAGE_NUM_TRIES    — It controls maximum number of attempt to perform an automatic operation

73. How to enable Flashcache compression?

Ans:

  • CellCLI> ALTER CELL flashCacheCompress=true

74. How many Exadata Storage Server Nodes are included in Exadata Database Machine X4-8?

Ans:

14 storage nodes

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75. Getting ready for an Exadata interview?

Ans:

Make sure to refresh your knowledge by reviewing this list of Exadata Interview questions.

76. What are the key Hardware components?

Ans:

  • DB Server
  • Storage Server Cells
  • High Speed Infiniband Switch
  • Cisco Switch

77. What are the Key Software Features?

Ans:

  • Smart Scan,
  • Smart Flash Cache
  • Storage Index
  • Exadata Hybrid Columnar Compression (EHCC)

IORM (I/O Resource Manager)

78. What is IORM?

Ans:

  • IORM stands for I/O Resource Manager.
  • It manages the I/O demand based on the configuration, with the amount of resources available. It ensures that none of the I/O cells become oversubscribed with the I/O requests. This is achieved by managing the incoming requests at a consumer group level.
  • Using IORM, you can divide the I/O bandwidth between multiple databases.
  • To implement IORM resource groups, consumers and plans need to be created first.

79. What types of operations does Exadata “offload”?

Ans:

Some of the operations that are offloaded from the database host to the cell servers are:

  • Predicate filtering
  • Column project filtering
  • Join processing
  • Backups

80. What is Exadata in brief?

Ans:

exadata is pre-configured combination of hardware and software which provides a platform to run the Oracle Database

81. What are the types of EHCC?

Ans:

  • very Low
  • very High
  • Archive High
  • Archive Low

82. What is the difference between write-through and write-back flash cache mode?

Ans:

  • write through –> Flash Cache will be used only for reading purposes.
  • writeback –> Flashcache will be used for both reading and writing.

83. What is the smart flash cache?

Ans:

Flash cache is the PCIe (Peripheral Components Interconnect Express) card which is plugged into the back end of the storage cell.

84. How does a smart scan work?

Ans:

  • If any query executes on the database server then the database server sends the extents and metadata to the storage cell.
  • A smart scan will scan data blocks to identify relevant rows and columns.
  • Once data identified by a smart scan, it will return to the database with only appropriate rows and columns.
  • Once the DB server gets the data, it will assemble the returned data into the result set.
  • This operation will save the bandwidth as well as CPUs and memory costs on the database server as whole SL processing happens on the storage server.

85. What are the prerequisites to configure ASR?

Ans:

  • Access to My Oracle Support
  • Internet connectivity using HTTPS
  • Network connectivity from ASR server to Exadata components

86. Which MOS ID I should refer to for the latest patch update?

Ans:

MOS 888828.1

87. Which tool is used to generate initial configuration files based on customer data?

Ans:

OEDA (Oracle Exadata Deployment Assistance)

88. Which all networks are available in Exadata?

Ans:

  • Infiniband Network
  • ILOM and Management Network
  • Client/Public Network

89.What are the Exadata Health check tools available?

Ans:

  • Exachk
  • sundiagtest
  • oswatcher
  • OEM 12c

90. What is the client or public network in Exadata?

Ans:

A client or public network is used to establish connectivity between database and application.

91.What are the steps involved in the initial Exadata configuration?

Ans:

Initial network preparation

  • Configure Exadata servers
  • Configure Exadata software
  • Configure database hosts to use Exadata
  • Configure ASM and database instances
  • Configure ASM disk group for Exadata

92. What is the iDB protocol?

Ans:

iDB stands for intelligent database protocol. It is a network-based protocol that is responsible to communicate between storage cell and database server.

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