IBM Netezza Interview Questions
What is Netezza?
IBM Netezza is a datawarehouse appliance in which both h/w and s/w are tightly coupled to deliver best performance to the business.
Appliance is like a black box. For ex: Washing machine.
List various datawarehouse appliances available in the market? (or) who are all Netezza’s competitors?
-Microsoft Parallel machine.
Netezza (vs) Hadoop:
Hadoop: For Unstructured data. For ex: Someone wishing you on your birthday
Netezza: Structured data. Registering for a facebook account.
List various appliance components
-Sub components: 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
List few ETL tools?
Informatica, Datastage, Ab intio
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List few BI tools?
Cognos, OBIEE, SSIS
Where system catalog information is stored? In Netezza host or Netezza disks?
For example: when we create a table, table definition is stored in host disks (df -k) and rows/records of this table are stored in Netezza disks
What are default userid’s and passwords in Netezza?
root, nz, admin.
What is clustering in Netezza?
Clustering is nothing but 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.
List few back slash commands in Netezza
Back slash commands: To avoid basic day to day SQL
For example: \du is to display users. \l is to list the database users.
What is the difference between “nzsql” and “nzsql -E”
-E ==> To see the underlying query generated by back slash command.
List 2 default databases in Netezza
MASTER_DB: Is template database; helps us to create new databases faster.
What is the extent and page size in Netezza?
Extent size: 3MB
Page size: 128 KB
Note: The above are fixed. we can’t change them.
What are various maximums in Netezza?
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
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List few environment variables in Netezza
List constraints in Netezza
Primary Key (Not enforced)
Unique key (Not enforced)
Referential Integrity (Not enforced)
Not Null (Enforced)
Data type verification (Enforced)
Techniques to improve Netezza appliance performance?
As a developer:
– At design time, have a best distribution key. To avoid data skew
– Use appropriate data types. For example: If INT2 is good, then don’t use INT4. For age, Byteint (Int1) is good enough
What is a Snippet?
Snippet is a part of given query. When we submit a query to Netezza, it is divided into multiple snippets. These snippets are executed by Snippet(s)-Blades.
How do you change distribution key of already create table?
CTAS: Create table as …