Oracle Exadata Database Interview Questions & Answers

Question 1. What Are The Different Exadata Configurations?

Answer :

• The Exadata Appliance configuration comes as a Full Rack, Half Rack or Quarter Rack.
• The Full Rack X2-2 has 6 CPUs per node with Intel Xeon 5670 processors and a total of 8 Database Server nodes, also known as compute 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

Question 2. What Are The Key Oracle Exadata Features?

Answer :

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).

Question 3. What Is A Cell And Grid Disk?

Answer :

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.

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.

Question 4. What Is Iorm?

Answer :

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 e created.

Question 5. What Is Hybrid Columnar Compression?

Answer :

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.

Question 6. What Is Flash Cache?

Answer :

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 reduces data acess 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.

Question 7. What Are The Parallelism Instance Parameter Used In Exadata?

Answer :

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

Question 8. What Are The Ways To Migrate Onto Exadata?

Answer :

Depending on the downtime allowed there are several options:
• Traditional Export/Import
• Oracle DataGuard
• Tablespace transportation.
• Goldengate Replication after a data restore onto Exadata.

Question 9. What Is Exadata?

Answer :

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

Question 10. What Is Storage Index And How It Works?

Answer :

• 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 filter out data from the consideration.

Question 11. Which Protocol Used By Asr To Send Notification?

Answer :

SNMP : Simple Network Management Protocol

Question 12. What Are The Options To Update Cell_flashcache For Any Object?

Answer :

• KEEP
• DEFAULT
• NONE

Question 13. What Is The Default Size Of Smart Flash Log?

Answer :

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

Question 14. What Is Flash Cache And How It Works?

Answer :

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.

Question 15. How Many Exadata Storage Server Nodes Are Included In Exadata Database Machine X4-8?

Answer :

14 storage nodes

Question 16. What Is The Difference Between Dbrm And Iorm?

Answer :

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

Question 17. What Are The Three Major Components Of Exadata Database Server?

Answer :

• Database Instance
• ASM Instance
• Database Resource Manager

Question 18. What Is The Difference Between An Exadata X3-2 Machine And An Exadata X3-8 Machine?

Answer :

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

Question 19. How Many Exadata Wait Events Contained In 11.2.0.3 Release?

Answer :

There are 53 wait events are exadata specific events.

Question 20. Which Disk Group Is Used To Keep Ocr Files On Exadata?

Answer :

+DBFS_DG

Question 21. Which Statistic Can Be Used To Check Flash Hit Ration On Database Level?

Answer :

Cell flash cache read hits

Question 22. How To Enable Flashcache Compression?

Answer :

CellCLI> ALTER CELL flashCacheCompress=true

Question 23. Which Migration Methodology Available If Want To Migrate From High Endian To Low Endian Os Architecture?

Answer :

1. Golden Gate
2. Transportable Tablespace
3. Incremental Transportable Tablespace
4. Data Pump

Question 24. How Much Time Required To Apply Bundle Patch On Half Rack Exadata Database Machine With Rolling Option?

Answer :

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

Question 25. Which Network Is Used For Rac Inter-connectivity?

Answer :

Infiniband Network

Question 26. What Are The Steps To Create Dbfs?

Answer :

STEPS :

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

Question 27. What Is Grid Disk?

Answer :

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.

Question 28. When One Should Execute Exacheck?

Answer :

Before and after any configuration change in Database Machine

Question 29. What Is The Difference Between High Capacity And High Performance Disk?

Answer :

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

Question 30. What Is The Capacity Of Infiniband Port?

Answer :

40 Gbps

Question 31. Which Feature Of Exadata Is Used To Eliminate Disk Io?

Answer :

Flash Cache

Question 32. What Is The Difference Between Wright-through And Write-back Flashcache Mode?

Answer :

• writethrough --> Falshcache will be used only for reading purpose.
• writeback --> Flashcache will be used for both reading and writing.

Question 33. How To Take Cell Storage Software Backup?

Answer :

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

Question 34. What Is The Command To Enable Query High Compression On Table?

Answer :

SQL>alter table table_name move compress for query high;

Question 35. How Many Networks Required In Exadata?

Answer :

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

Question 36. How We Can Check Whether Oracle Best Practice Has Been Configured On Exadata?

Answer :

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

Question 37. What Is Iorm And What Is Its Role In Exadata?

Answer :

IORM stand for I/O Resource Manager which manages the I/Os of multiple database on storage cell.

Question 38. What Is The Difference Between Cellcli And Dcli?

Answer :

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

Question 39. What Is Offloading And How It Works?

Answer :

It refers to the fact that part of the traditional SQL 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.

Question 40. What Is Ehcc?

Answer :

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

Question 41. What Are The Exadata Health Check Tools?

Answer :

• Exacheck
• sundiagtest
• oswatcher
• OEM 12c

Question 42. Where We Can Define Which Cell Storage Can Be Used By Particular Database Server?

Answer :

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

Question 43. How To Upgrade Firmware Of Exadata Components?

Answer :

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

Question 44. How To Integrate Exadata With Oem 12c?

Answer :

• 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

Question 45. What Is Asr?

Answer :

• ASR is the tool to manage the Oracle hardware. Full form of ASR is Auto Service Request.
• Whenever any hardware fault occurs ASR automatically raise SR in Oracle Support and send notification to respective customer.

Question 46. Which Os Is Supports In Exadata?

Answer :

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

Question 47. Which Protocol Used For Communication Between Database Server And Storage Server?

Answer :

The protocol used for communication between database server and storage server is  : iDB protocol

Question 48. How Many Cell Storage Comes In Full Rack Exadata Machine?

Answer :

There are 14 cell storage comes in full rack exdata machine.

Question 49. How To Replace Faulty Hdd In Exadata Storage?

Answer :

All the HDD are hot swapable so if we are using proper redundacny than we can direct remove and replace new HDD.

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

Question 50. What Is The Purpose Of Spine Switch?

Answer :

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