Oracle Exadata Interview Questions
Oracle Exadata Interview Questions
Q. What is Exadata?
Exadata is pre-configured combination of hardware and software which provides a platform to run the Oracle Database.
Q. Why I should go for Exadata?
There are multiple reason to answer this question. You can go to this link for detailed answer
Q. Key components of Exadata
- DB Server
- Cell Storage
- Infiniband Switch
- Cisco Switch
Q. Features of Exadata
- Smart Scan
- Smart Flash Cache
- Storage Index
- EHCC (Exadata Hybrid Columnar Compression)
Q. Exadata Sizing
Exadata comes in follwing configuration
- Full Rack
- Half Rack
- Quater Rack
- 1/8th Rack
Q. What is storage index and how it works?
- 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.
Q. Which protocol used by ASR to send notification?
Q. Is manually intervance possible in storage index?
Q. What are the options to update cell_flashcache for any object?
Q. What is the default size of smart flash log?
512MB per module.
Each storage cell having 4 modules so its 4X512 MB per CELL
Q. What is flash cache and how it works?
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.
Q. What is cellcli?
cellcli – It is cell command line utility. We can manage cell storage with the use of cellcli utility. We can say it’s utility to administer cell storage.
Q. Types of EHCC:
- Query Low
- Query High
- Archive High
- Archive Low
Q. Which package can be used to estimate the compression ration of table?
Q. Background services of Cell Server
MS- Management Server
cellsrv – Cell Server
RS – Restart Server
Q. How to replace faulty HDD in Exadata Storage?
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.
Q. How many disk comes with in a storage cell?
Q. What is the purpose of spine switch?
Spine switch is used to connect or add more Exadata machine in the cluster
Q. How to migrate database from normal setup to Exadata ?
There many methods we can use to migrate DB to Exadata. Below are some of them.
- 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.
Q. Exadata shutdown and start-up procedure
Stop Database and Listener
Shutdown Database Servers
Shutdown Cell Storage
Shutdown all the switches
Remove powers from PDUs
Start-up procedure would be in reverse order.
Q. How many database servers comes in 1/8th rack and quarter rack?
Q. How many cell storage comes in full rack exadata machine?
Q. Can we use flash disk as ASM disk?
Q. Which protocol used for communication between database server and storage server?
Q. Which OS is supports in Exadata?
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.
Q. What is ASR?
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.
Q. How to integrate Exadata with OEM 12c?
- 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
Q. How to upgrade firmware of Exadata components?
It can be done through ILOM of DB or Cell server.
Q. Where we can define which cell storage can be used by particular database server?
CELLIP.ORA file contains the list of storage server which is accessed by DB server.
Q. What are the Exadata Health check tools?
- OEM 12c
Q. What is EHCC?
EHCC is Exadata Hybrid Columnar Compression which is used to compress data in the Database.
Q. What is offloading and how it works?
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.
Q. What is the difference between cellcli and dcli?
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.
Q. What is IORM and what is its role in Exadata?
IORM stand for I/O Resource Manager which manages the I/Os of multiple database on storage cell.
Q. How we can check whether oracle best practice has been configured on Exadata?
We can execute Exacheck and verify the best practice setup on Exadata machine.
Q. How many networks required in Exadata?
- Public/Client Network — For Application Connectivity
- Management Network — For Exadata H/W management
- Private Network — For cluster inter connectivity and Storage connectivity
SQL>alter table table_name move compress for query high;
Q. How to take cell storage software backup?
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.
Q. What is the difference between wright-through and write-back flashcache mode?
- writethrough –> Falshcache will be used only for reading purpose
- writeback –> Flashcache will be used for both reading and writing
Q. Which feature of Exadata is used to eliminate disk IO?
Q. What is the capacity of Infiniband port?
Q. What is the difference between high capacity and high performance disk?
- High capacity disk comes with more storage space and less rpm (7.5k)
- High Performance disk comes with less storage and high rpm (15k)
Q. When one should execute Exacheck?
Before and after any configuration change in Database Machine
Q. What is grid disk?
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.
Q. Which network is used for RAC inter-connectivity?
Q. What are the steps to create DBFS?
- 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
Q. Which migration methodology available if want to migrate from high endian to low endian OS architecture?
- Golden Gate
- Transportable Tablespace
- Incremental Transportable Tablespace
- Data Pump
Q. How much time required to apply bundle patch on Half rack Exadata Database Machine with rolling option?
Approximate 3 hours per Cell and DB server including Infiniband & PDU patching required 1 hour each
Q. What benefit we can get if we apply bundle patch on exadata in rolling fashion while ASM configured with high redundancy?
It will reduce the risk of storage disk failure
Q. Advantages and disadvantages of rolling and non-rolling patching on Exadata Database Machine.
No downtime required
- It takes more time to apply bundle patches
- If ASM is on normal redundancy than disk failure on another Cell could lead to the DB corruption.
- Less time required to do the patching
- It could eliminate the risk of single disk failure if ASM configured with normal redundancy
Downtime required while applying bundle patch.
Q. Which ASM parameters are responsible for Auto disk management in Exadata?
_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
Q. How to enable Flashcache compression?
CellCLI> ALTER CELL flashCacheCompress=true
Q. Which statistic can be used to check flash hit ration on database level?
Cell flash cache read hits
Q. Which disk group is used to keep OCR files on Exadata?
Q. How many Exadata wait events contained in 126.96.36.199 release?
There are 53 wait events are exadata specific events.
Q. What is the difference between an Exadata X3-2 machine and an Exadata X3-8 machine?
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.
Q. What are the three major components of Exadata database server?
Database Resource Manager
Q. What is the difference between DBRM and IORM?
DBRM is the feature of database while IORM is the feature of storage server software.
Q. How many Exadata Storage Server Nodes are included in Exadata Database Machine X4-8?
14 storage nodes
Q. What are the different Exadata configurations?
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
Q. What are the key Oracle Exadata Features?
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)
Q. What is a Cell and Grid Disk?
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.
Q. What is Flash cache?
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 mechanism to reduces 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.
Q. What is Smart Scan?
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.
Q. What are the Parallelism instance parameter used in Exadata?
The parameter PARALLEL_FORCE_LOCAL can be specified at the session level for a particular job.
Q. What are the ways to migrate onto Exadata?
- Depending on the downtime allowed there are several options:
- Traditional Export/Import
- Oracle DataGuard
- Tablespace transportation.
- Goldengate Replication after a data restore onto Exadata.
Q. What operating systems does Exadata support?
Exadata has traditionally run Oracle Linux OS. Recently, Solaris has also been made available on this engineered system.