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Here are frequently asked Oracle Exadata Interview Questions, let's have a look into them.
Oracle Exadata Interview Questions
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) Key components of Exadata
1. DB Server
2. Cell Storage
3. Infiniband Switch
4. Cisco Switch
Q3) Features of Exadata
1. Smart Scan
2. Smart Flash Cache
4. Storage Index
5. EHCC (Exadata Hybrid Columnar Compression)
Q4) Exadata Sizing
Ans: Exadata comes in the following configuration
1. Full Rack
2. Half Rack
3. Quater Rack
4. 1/8th Rack
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Q5) What is a storage index and how it works?
Ans: 1. 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).
2. Storage Indexes are stored in memory only and are never written to disk.
3. Storage Index filters out data from the consideration.
Q6) Which protocol used by ASR to send notifications?
Q7) Is manual intervention possible in the storage index?
Q8) What are the options to update cell_flashcache for any object?
Q9) What is the default size of the smart flash log?
Ans: 512MB per module.
Each storage cell having 4 modules so its 4X512 MB per CELL
Q10) 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 reading and writes operations.
The primary task of a smart flash cache is to hold frequently accessed data in the flash cache so next time if the same data required then physical read can be avoided by reading the data from the flash cache.
Q11) What is cellcli?
Ans: cellcli – It is a cell command-line utility. We can manage cell storage with the use of cellcli utility. We can say it’s a utility to administer cell storage.
CELLCLI-ALTER CELLCLI-CREATE CELLCLI-DROP CELLCLI-LIST
Q12) Types of EHCC:
1. Query Low
2. Query High
3. Archive High
4. Archive Low
Q13) Which package can be used to estimate the compression ratio of the table?
Q14) Background services of Cell Server
Ans: MS- Management Server
cellsrv – Cell Server
RS – Restart Server
Q15) 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 direct remove and replace the new HDD.
Storage software will take care of all the stuff in the background after replacing the HDD.
Q16) How many disks come within a storage cell?
Q17) What is the purpose of the spine switch?
Ans: Spine switch is used to connect or add more Exadata machine in the cluster
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Q18) How to migrate the database from the normal setup to Exadata?
Ans: Their many methods we can use to migrate DB to Exadata. Below are some of them.
2. Physical Standby
3. Logical Standby
4. Transportable Tablespace
5. Transportable Database
6. Golden gate
7. RMAN cold and hot backup restoration
8. Oracle Streams
The use of the migration method totally depends on source setup as well as downtime consideration.
Q19) Exadata shutdown and start-up procedure
Ans: Shutdown Procedure:
Stop Database and Listener
Shutdown Database Servers
Shutdown Cell Storage
Shutdown all the switches
Remove powers from PDUs
The start-up procedure would be in reverse order.
Q20) How many database servers come in 1/8th rack and quarter rack?
Q21) How many cell storage comes in full rack Exadata machine?
Q22) Can we use a flash disk as an ASM disk?
Q23) Which protocol used for communication between the database server and storage server?
Ans: iDB protocol
Q24) 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.
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Q25) 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.
Q26) How to integrate Exadata with OEM 12c?
Ans: 1. Install OEM agent on DB server
2. Launch auto-discovery with the use of One Command XML file
3. Specify the required credentials for all the components
4. Review Configuration
5. Complete the setup
Q27) How to upgrade the firmware of Exadata components?
Ans: It can be done through ILOM of DB or Cell server.
Q28) Where we can define which cell storage can be used by a particular database server?
Ans: CELLIP.ORA file contains the list of storage server which is accessed by DB server.
Q29) What are the Exadata Health check tools?
Ans: 1. Exacheck
4. OEM 12c
Q30) What is EHCC?
Ans: EHCC is Exadata Hybrid Columnar Compression which is used to compress data in the Database.
Q31) What is offloading and how it works?
Ans: 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.
Q32) 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 storages as well as DB servers.
Q33) 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 storage cell.
Q34) How we can check whether oracle best practice has been configured on Exadata?
Ans: We can execute Exacheck and verify the best practice setup on the Exadata machine.
Q35) How many networks required in Exadata?
Ans: 1. Public/Client Network — For Application Connectivity
2. Management Network — For Exadata H/W management
3. Private Network — For cluster interconnectivity and Storage connectivity
Q36) What is the command to enable query high compression on the table?
Ans: SQL>alter table table_name move compress for query high;
Q37) 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 Cell boot Flash Drive to take a backup of software.
Q38) What is the difference between wright-through and write-back flash cache mode?
Ans: 1. write-through –> Falshcache will be used only for reading purpose
2. writeback –> Flashcache will be used for both reading and writing
Q39) Which feature of Exadata is used to eliminate disk IO?
Ans: Flash Cache
Q40) What is the capacity of the Infiniband port?
Ans: 40 Gbps
Q41) What is the difference between high capacity and high-performance disk?
Ans: 1. The high capacity disk comes with more storage space and less rpm (7.5k)
2. High-Performance disk comes with less storage and high rpm (15k)
Q42) When one should execute Exacheck?
Ans: Before and after any configuration change in Database Machine
Q43) What is a 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.
Q44) Which network is used for RAC inter-connectivity?
Ans: Infiniband Network
Q45) What are the steps to create DBFS?
Ans: 1. Create Directory
2. Create Tablespace on a database that you are going to use for DBFS
3. Create a user for DBFS
4. Grant required privileges to a created user
5. Now connect to the database with the created user
6. Create dbfs filesystem by invoking dbfs_create_filesystem_advanced
7. Mount file system by starting dbfs_client
Q46) Which migration methodology available if want to migrate from high endian to low-endian OS architecture?
Ans: 1. Golden Gate
2. Transportable Tablespace
3. Incremental Transportable Tablespace
4. Data Pump
Q47) 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.
Q48) 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 provides a mechanism to reduces data access latency by retrieving data from memory rather than having to access data from disk. Total flash storage of 384GB per cell is available on the Exadata appliance.
Q49) What is a 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 to filter 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.
Q50) What is the Parallelism instance parameter used in Exadata?
Ans: The parameter PARALLEL_FORCE_LOCAL can be specified at the session level for a particular job.
Q51) What are the ways to migrate onto Exadata?
Ans: 1. Depending on the downtime allowed there are several options:
2. Traditional Export/Import
3. Oracle DataGuard Interview Questions
4. Tablespace transportation.
5. Goldengate Replication after a data restore onto Exadata.
Q52) 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.
Q53) Which statistic can be used to check flash hit ratio on database level?
Ans: Cell flash cache read hits
Q54) Which disk group is used to keep OCR files on Exadata?
Q55) How many Exadata wait for events contained in the 22.214.171.124 release?
Ans: There are 53 wait events that are Exadata specific events.
Q56) What is the difference between an Exadata X3-2 machine and an Exadata X3-8 machine?
Ans: 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.
Q57) What are the three major components of the Exadata database server?
Ans: Database Instance
Database Resource Manager
Q58) 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.
Q59) What are the different Exadata configurations?
Ans: The Exadata Appliance configuration comes as a Full Rack, Half Rack or Quarter Rack.
The Full Rack X2-2 has 6 CPU’s 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 CPU’s 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
Q60) What are the key Oracle Exadata Features?
Ans: Some of the key hardware and software features are:
1. Hardware level
2. Storage Server Cells
3. High-Speed Infiniband Switch
4. Software level
5. Smart Scan,
6. Flash Cache
7. Hybrid Columnar Compression
8. IORM (I/O Resource Manager)
Q61) How much time required to apply a bundle patch on a Half rack Exadata Database Machine with a rolling option?
Ans: Approximate 3 hours per Cell and DB server including Infiniband & PDU patching required 1 hour each
Q62) What benefit we can get if we apply a bundle patch on Exadata in a rolling fashion while ASM configured with high redundancy?
Ans: It will reduce the risk of storage disk failure
Q63) Advantages and disadvantages of rolling and non-rolling patching on Exadata Database Machine.
No downtime required
1. It takes more time to apply bundle patches
2. If ASM is on normal redundancy than disk failure on another Cell could lead to the DB corruption.
1. Less time required to do the patching
2. It could eliminate the risk of single disk failure if ASM configured with normal redundancy
Downtime required while applying the bundle patch.
Q64) Which ASM parameters are responsible for Auto disk management in Exadata?
Ans: AUTO_MANAGE_MAX_ONLINE_TRIES — It controls the maximum number of attempts to make disk Online
AUTO_MANAGE_EXADATA_DISKS — It controls the auto disk management feature
AUTO_MANAGE_NUM_TRIES — It controls the maximum number of attempt to perform an automatic operation
Q65) How to enable Flash cache compression?
Ans: CellCLI> ALTER CELL flashCacheCompress=true
Q66)How many Exadata Storage Server Nodes are included in Exadata Database Machine X4-8?
Ans: 14 storage nodes