Oracle Exadata Interview Questions

1. 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 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

2. 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)

3. 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.

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.

4. What is IORM?
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.

5. What is hybrid columnar compression?
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.
6. 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 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.

7. What is Smart Scan?

8. What are the Parallelisim instance parameter used in Exadata?
The parameter PARALLEL_FORCE_LOCAL can be specified at the session level for a particular job.

9. 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.