IBM Netezza Interview Questions

IBM Netezza Interview Questions and Answers

Q1) What is Netezza?

Ans:

• IBM Netezza is a data warehouse appliance in which both h/w and s/w are tightly coupled to deliver the best performance to the business.
• The appliance is like a black box. Forex: Washing machine.

Q2) List various data warehouse appliances available in the market? (or) who are all Netezza’s competitors?

Ans: 

• Oracle Exadata
• Teradata
• EMC Greenplum
• HP Vertica
• Microsoft Parallel machine.

Q3) Netezza (vs) Hadoop:

Ans:

• Hadoop: For Unstructured data. Forex: Someone wishing you on your birthday
• Netezza: Structured data. Registering for a Facebook account.

Q4) List various appliance components?

Ans: 

• SMP Hosts
• Disks
• Snippet Blades
• Subcomponents: Disk Enclosures, SPA, SPU, FPGA

S-Blade = SPU

Storage Array 1, Storage Array 2.

Each Storage Array has 4 disk Enclosures. Each Disk Enclosure contains 12 disks of 1TB size.

Each S-Blade owns several disks, which reside in a storage array within the same rack.

Storage Array = Storage Disk = N disk enclosures

Storage Array 1  +  Chassis 1 => Snippet Processing Array (SPA) 1

Sorage Array2    + Chassis 2 => SPA 2

Q5) List a few ETL tools?

Ans: Informatica, Datastage, Ab intio

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Q6) List a few BI tools?

Ans: Cognos, OBIEE, SSIS

Q7) Where system catalog information is stored? In Netezza host or Netezza disks?

Ans: Netezza hosts.

For example: when we create a table, the table definition is stored in host disks (df -k) and rows/records of this table are stored in Netezza disks

Q8) What are default user-id's and passwords in Netezza?

Ans:  root, nz, admin.

Q9) What is clustering in Netezza?

Ans: Clustering is nothing but a grouping of similar things.  In Netezza, we have 2 SMP hosts. These 2 hosts are part of a cluster. In this cluster, one host is active and another host is passive.

Q10) List a few backslash commands in Netezza?

Ans: Backslash commands: To avoid basic day to day SQL

For example, du is to display users. l is to list the database users.

Q11) What is the difference between “nzsql” and “nzsql -E”

Ans: E ==> To see the underlying query generated by the backslash command.

Q12) List 2 default databases in Netezza?

Ans: SYSTEM, MASTER_DB

MASTER_DB: This is a template database; helps us to create new databases faster.

Q13) What is the extent and page size in Netezza?

Ans:

• Extent size: 3MB
• Page size: 128 KB

Note: The above are fixed. we can’t change them.

Q14) What are various maximums in Netezza?

Ans:

• Columns: 1600 per table or view
• Maximum columns per distribution: 4
• Max Length of database and column names: 128 bytes
• Max number of characters in a char/varchar field: 64,000
• Max connections to the server: 2000. Default: 500
• Row size: 65,535 bytes

IBM Netezza Tutorial

Q15) List a few environmental variables in Netezza?

Ans:

• NZ_DATABASE
• NZ_HOST
• NZ_USER
• NZ_PASSWORD

Q16) List constraints in Netezza

Ans:

• Primary Key (Not enforced)
• Unique key (Not enforced)
• Referential Integrity (Not enforced)
• Not Null (Enforced)
• Data type verification (Enforced)

Q17) Techniques to improve Netezza appliance performance?

Ans: As a developer:

At design time, have the best distribution key. To avoid data skew

Use appropriate data types. For example: If INT2 is good, then don’t use INT4. Forage, Byteint (Int1) is good enough

Q18) What is a Snippet?

Ans: Snippet is a part of the given query. When we submit a query to Netezza, it is divided into multiple snippets. These snippets are executed by Snippet(s)-Blades.

Q19) How do you change the distribution key of already creating a table?

Ans: CTAS: Create a table as …