Oracle Exadata Interview Questions

What do you know about Exadata? Specify the advantages of using Exadata?

Ans: Exadata in Oracle refers to the pre-configured combination of software and hardware specifically designed to provide a platform to run the Oracle database. Oracle Exadata is a modern framework intended to run the databases and scale-out the database servers.

Advantages of Oracle Exadata:

Oracle Exadata includes an Exadata cluster that is compatible to deliver a consistent performance along with increased throughput. Oracle Exadata uses inter-instance and inter-instance parallelism that results in consistency though the load increases on the cluster.

Explain the features of Exadata?

Ans: Oracle Exadata is configured with many features in it. The features of Oracle Exadata are listed below:

Smart Scan: Smart scan in Exadata is a unique feature capable of enhancing the database's performance as many times as needed. A smart scan helps in processing the queries and intelligently retrieves specific rows in the table.It applies to filter criteria and column projection, which is selection criteria.

Smart Flash Cache: The smart flash cache is a hardware component that delivers high performance configured in the Exadata storage cell server. The performance improved by using the read and write operations. Smart flash cache helps in holding the frequently accessed data. This would help in easy access whenever the users need the same data. This helps in avoiding the physical read by allowing the data to be read from the physical cache.

IORM: IORM refers to Input/output Resource Manager. IORM is specifically used to manage the I/O using the configuration information with the number of resources available. It helps in maintaining the incoming requests at a consumer group level.

Storage Index: Storage index is one of the features in the Exadata database machine, which is used to reduce the I/O amount for an Exadata smart scan.

EHCC: EHCC refers to Exadata Hybrid Columnar Compression, which helps in compressing the data at the column level in a table. It helps create the compression data units, including logical grouping of the columns from the available multiple rows.

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List the key hardware components of Exadata? How do you test the performance of Exadata?

Ans: The following are the key hardware components of Exadata.

• Database server
• High-speed InfiniBand switch
• Cisco switch
• Storage Server cells

The performance of Exadata can be tested using the calibrate commands at the cellcli command line.

How to upgrade the firmware of Exadata components?

Ans: The firmware of the Exadata components can be upgraded using the ILOM of the database or cell server.

Explain the term ASR? What are the prerequisites to be followed to configure ASR?

Ans: ASR refers to Auto Service request, a tool that is designed to manage the Oracle hardware. The Auto service request tool will automatically raise a service request when any issues arise with respect to the hardware. Based on the request sent, it will send the appropriate notification to respective customers.

The following are the prerequisites to be followed to configure ASR:

• Access is required to My Oracle Support
• Establishment of internet connectivity using HTTPS
• Establishment of network connectivity from the ASR server to the Exadata components

Which environment do you think is the good fit for Exadata? Briefly explain the different Exadata configurations?

Ans: Exadata is good for the environment, which includes data warehouses. Further, the enhancement is done to be used in the OLTP databases as well.

• There are different Exadata configurations designed by Exadata. They are Full Rack, Half Rack, or Quarter Rack.
• The Full Rack configuration includes 6 CPUs per node, Intel Xeon 5670 processor, eight database server nodes. 
• The Half Rack configuration includes 6 CPUs per node, Intel Xeon 5670 processor, four database server nodes.

Explain what you mean by cell and grid disk? How do you obtain information on the cell disks? Can I have multiple cell disk for one grid disk?

Ans: Cell and grid disk represents the logical part of the Exadata storage. The disk drives are used to store the data. Cell disk is the combination of all the disks together to store the user data. Every cell disk is linked with the logical unit, which includes 12 hard disk drives that are mapped to it. Grid Disks are presented to the ASM and ASM disks that are built upon the cell disks. Grid disks include the space allocation that is available in the outer tracks of the cell in chunks.

The list cell disk command can be issued at the cellcli command to obtain the information on the cell disk.No, Cell disk can have multiple grid disk, but grid disk cannot have various cell disk.

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What is meant by a storage index? Give a brief explanation of the working of the storage index? Is manually intervening possible in the storage index?

Ans: Storage index is the feature available in Exadata used to reduce the amount of I/O required to service the requests. The storage index includes both maximum and minimum value, upto eight columns. Storage indexes are never written to the disks and they are used to filter the required data. Storage indexes can be stored only in memory. No, it is not possible to intervene in the storage index.

What are the options available to update the Cell_flashcache for any object? How do you enable the Flashcache compression?

Ans: There are three different options available to update the cell_flashcache for any object. They are listed below:

• DEFAULT
• KEEP
• NONE

The Cell_flashcache compression is enabled by using the following command: CellCLI>ALTER CELL flashCacheCompress=true.

. What are the different ways available to migrate onto Exadata?

Ans: Multiple ways are available to migrate onto Exadata. These are dependent on the downtime. They are listed below:

• Oracle DataGuard
• Tablespace transportation
• Traditional Export/import
• Goldengate Replication after the data is restored onto the Exadata.

. Why is cellcli used? Explain the difference between dcli and cellcli?

Ans: Cellcli refers to the cell command-line utility. By using the cellcli utility, cell storage can be managed. It is the cell storage that is used to administer the cell storage. It includes different commands like CELLCLI-ALTER, CELLCLI-CREATE, CELLCLI-LIST, CELLCLI-DROP.

DCLI refers to the distributed command-line utility. It is the command-line utility specifically designed to replicate command on database servers and multiple storage.

. What are the different networks available in Exadata? What are the different operating systems that Exadata supports?

Ans: There are three different networks available in Exadata. They are listed below:

• Management network: management network specifically used or Exadata hardware management
• Public/Client network: Public or client network specifically used for application connectivity requirements.
• Private network: The private system specifically used for storage connectivity and cluster interconnectivity.
• Exadata is designed to provide its extensive support for operating systems like the Linux operating system and Solaris.

. Differentiate between IORM and DBRM?

Ans: DBRM stands for database request module, a traditional database model that allows representation of SQL statements in a serial format in a program.

IORM stands for Input/Output (I/O) Resource is a tool specifically designed for management of the multiple databases and workloads by sharing the I/O resources of the Oracle Exadata System Software. 

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. What is DBFS? What are the steps to be followed to create DBFS?

Ans: DBFS stands for Database File System, which helps create a standard interface represented in the form of files and directories in the database tables.

The following are the steps to be followed to create DBFS.

• Creation of directory
• Creation of tablespace on the database that you are going to use for the Database file system.
• User creation for the Database file system.
• Grant or give the required permissions or privileges to the user profile that has been created.
• Establishing connectivity with the database to the created user.
• Creation of the dbfs file system by invoking dbfs_create_filesystem_advanced
• Mounting of the system by starting dbfs_client

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

Ans: The following is the migration methodology that is available to migrate from high endian to low endian OS architecture.

• Golden gate
• Transportable tablespace
• Incremental transportable tablespace
• Data pump.

. What do you mean by EHCC? What are the different types of EHCC available?

Ans: EHCC refers to Exadata Hybrid Columnar Compression used to perform compression of the data in the database. There are different types of EHCC available. They are listed below:

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

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. What is smart scan offloading and offload block filtering?

Ans:

Smart Scan Offloading: Exadata Smart scan offloading allows the processing of the queries from the database server to the storage server. The Exadata storage servers consist of the processors that will perform data processing. The data that is requested will be shared and returned to the database server.

Offload Block filtering: Offload block filtering is an option available in the Exadata storage server that allows filtering of the blocks that are not required or utilized for the incremental backup. Using this, the required blocks of data backup are sent to the database.

.Which tool is used to generate initial configuration files based on the customer's data?

Ans: There is a tool designed to generate the initial configuration files based on the customer-related data called Oracle Exadata Deployment Assistance (OEDA).

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

Ans: The write-through is an option available to use the reading mode. In simple terms, write-through is used in the flash cache for reading purposes.

The write-back is the option available to be used in both reading and writing mode. In simpler terms, write-back is used in the flash cache to perform both reading and writing operations.

. What is the purpose of the spine switch?

Ans: The spine switch in Exadata is designed to establish connectivity or add more Exadata machines in the cluster. The Infiniband spine switch is used to connect and expand the Exadata racks.

. What are the Parallelism instance parameters used in Exadata?

Ans: The parallel instance parameter that is used in Exadata is PARAMETER_FORCE_LOCAL. This parameter is specified at the session level for a particular job.

. What is the secret behind Exadata's higher throughput?

. What do you know about the IDB protocol? List out the different health check tools that are available in Exadata?

Ans: IDB stands for Intelligent Database protocol that is designed to establish the connectivity or communication between the database server and the storage cell.

The following are the different health check tools available:

• Sundiag test
• Exachk
• OEM 12c
• Oswatcher

. Determine the capacity of Infiniband port? Which feature is available to eliminate the disk I/O in Exadata?

Ans: The capacity that could be handled in Infiniband port is 40Gbps.The flash cache is the feature that is available to eliminate the disk I/O in Exadata.

. Do you know what the default size of a smart flash log is?

Ans: The default size of the smart flash log is 512 MB per module.Each storage cell consists of 4 modules, so it will be 4* 512 MB per cell.

. List out the methods to be followed to migrate the database from the normal setup to Exadata?

Ans: Several methods can be followed to migrate the database from the normal setup to the Exadata. They are listed below:

• Physical standby
• Logical standby
• Oracle streams
• Transportable tablespace
• Transportable database
• RMAN cold and hot backup restoration
• Export/Import
• Golden gate

. Briefly explain or determine the steps to be followed to integrate the Exadata with OEM 12c?

Ans: The following are the steps to be followed to integrate the Exadata with OEM 12 c.

• Installation of OEM agent on the database server
• Launching of auto-discovery with the use of One command XML file
• Specifying the required credentials for all the components available
• Reviewing of the configuration
• Completion of the setup.

. Do you have an idea of the package in Exadata used to estimate the compression ratio of a table?

Ans: DBMS_COMPRESSION is the package that is available in Exadata to estimate the compression ratio of a table.

. What do you mean by LIBCELL? How many were Exadata wait events available in the 11.2.0.3 release?

Ans: LIBCELL in Exadata refers to Library Cell that is interlinked with the Oracle Kernel. LIBCELL helps in establishing the communication between the Oracle Kernel and the storage server. This communication establishment is network-based. It does not use the operating system reads and writes. 53 wait events are available in the 11.2.0.3 release.

. What do you mean by check ip? Explain why it is used?

Ans: Check ip in Exadata is an OS-based script. Checkip consists of the IP address and the hostname. Exadata uses this information in the configuration phase. It ensures that there is no IP duplication in the network by adding some pings to check. It also primarily checks the readiness of the network that includes DNS configuration.