Oracle Exadata Interview Questions

Following are some of the most frequently asked Oracle Exadata interview questions in the interview, here are the answers for them.

Q1) What is Exadata?

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

Q2) 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 writes operations.
  • The primary task of smart flash cache is to hold frequently accessed data in the flash cache so next time if the same data required than physical read can be avoided by reading the data from the flash cache.

Q3) What are the types of EHCC?

Ans:

  • Query Low
  • Query High
  • Archive High
  • Archive Low

Q4) What is the purpose of the spine switch?

Ans: A spine switch is used to connect or add more Exadata machine in the cluster

Q5) What is ASR?

Ans:

  • ASR is the tool to manage the Oracle hardware. The full form of ASR is the Auto Service Request.
  • Whenever any hardware fault occurs ASR automatically raises SR in Oracle Support and sends a notification to the respective customer.

Q6) 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 command on multiple storages as well as DB servers.

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Q7) What is the difference between wright-through and write-back flash cache mode?

Ans:

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

Q8) Exadata sizing configuration

Ans:

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

Q9) What are the steps to create DBFS?

Ans:

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

Q10) What is the difference between DBRM and IORM?

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

Q11) 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.

Q12) How smart scan works?

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 SQL processing happens on the storage server.

Q13) What are the pre-requisites to configure ASR?

Ans:

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

Q14) Which MOS ID I should refer to for the latest patch update?

Ans: MOS 888828.1

Q15) Which tool is used to generate initial configuration files based on customer data?

Ans: OEDA (Oracle Exadata Deployment Assistance)

Q16) What are the unique features of Exadata?

Ans:

  • Smart Scan (Cell Offload)
  • Flash cache
  • EHCC (Exadata Hybrid Columnar Compression)
  • IORM (IO Resource Manager)
  • Storage Index

Q17) Which all networks available in Exadata?

Ans:

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

Q18) What are the Exadata Health check tools available?

Ans:

  • Exacheck
  • sundiagtest
  • oswatcher
  • OEM 12c

Q19) What is the client or public network in Exadata?

Ans: A client or public network is used to established connectivity between database and application.

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Q20) 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

Q21) 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.

Q22) What is LIBCELL?

Ans: Libcell stands for Library Cell which is linked with Oracle kernel. It allows the oracle kernel to talk with the storage server via network-based instead of operating system reads and writes.

Q23) Which packaged is used by compression adviser utility?

Ans: DBMS_COMPRESSION package

Q24) What is the primary goal of the storage index?

Ans: Storage indexes are a feature unique to the Exadata Database Machine whose primary goal is to reduce the amount of I/O required to service I/O requests for Exadata Smart Scan.

Q25) What is smart scan offloading?

Ans: Offloading and Smart Scan are two terms that are used somewhat interchangeably. Exadata Smart Scan offloads the processing of queries from the database server to the storage server. Processors on the Exadata Storage Server process the data on behalf of the database SQL query. Only the data requested in the query are returned to the database server.

Q26) What is checkip and what the use of it?

Ans: Checkip is the OS level script that contains IP address and hostname which will be used by Exadata in the configuration phase. It checks network readiness like proper DNS configuration, it also checks there is no IP duplication in the network by pinging it which not supposed to ping initially.

Q27) Which script is used to reclaim the disk space of an unused operating system?

Ans: For Linux: reclaimdisks.sh For Solaris: reclaimdisks.pl

Q28) What should be ASM space allocation if backup performed internally?

Ans: 40% storage space allocation for DATA disk group 60% storage space allocation for RECO disk group

Q29) How database server communicates to the storage cells?

Ans: The database server communicates with the storage cells through the Infiniband network.

Q30) Can I have multiple cell disk for one grid disk?

Ans: No. Cell disk can have multiple grid disk but grid disk cannot have multiple cell disk

Q31) How many FMods available on each flashcard?

Ans: Four FMods (Flash Modules) are available on each flashcard.

Q32) Which processes are used by storage software?

Ans:

  • Cellsrv – Cell Server
  • MS- management server
  • RS – Restart Server

Q33) List the steps for replacing the damaged physical flash disk.

Ans:

  • Identify the damaged flash disk
  • Power off the cell
  • Replace flashcard
  • Power on the cell
  • Verify and confirm the new flashcard

Q34) What is a smart flash log?

Ans: A smart flash log is a temporary storage area on Exadata smart flash cache to store redoes log data.

Q35) Which parameter is used to enable and disable the smart scan?

Ans: cell_offload_processing

Q36) How to check infiniband topology?

Ans: We can verify infiniband switch topology by executing a verify-topology script from one of our database servers.

Q37) Can we use HCC on a non-Exadata environment?

Ans: No, HCC is only available data stored on the Exadata storage server.

Q38) What is a resource plan?

Ans: It is a collection of plan directives that determine how database resources are to be allocated.

Q39) What is DBFS?

Ans: DBFS stands for the Database File system which can be built on the ASM disk group using database tablespace.

Q40) What are the major steps involved for cell server patching?

Ans:

  • Check and note down the existing configuration of the cell
  • Clean up any previous patchmgr utility
  • Verify that the cells meet prerequisite checks
  • Patch cell server using patchmgr
  • Validation updated cell

Q41) What is the purpose of the Infiniband spine switch?

Ans: A spine switch is used to connect multiple Exadata database machines.

Q42) What is OEM?

Ans: OEM is Oracle Enterprise Manager which is a centralized tool to monitor and administer systems as well software.

Q43) What is offloaded block filtering?

Ans: Exadata storage server filters out the blocks that are not required for the incremental backup in progress so only the blocks that are required for the backup are sent to the database.

Q44) Which command is used to monitor BCT?

Ans: SQL>select filename,status, bytes from v$block_change_tracking;

Q45) How to add memory to the database server?

Ans:

  • Power off the database server
  • Add memory expansion into the server
  • Power on the server