What is Linear Scalability in Teradata?

Linear Scalability:
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Normally when size of the database increases the performance will decreases. But in Teradata designed  in such a way that size of the database increases the performance also increases due to parallelism .

What is the difference between Primary key and primary Index in Teardata?

Primary Key:
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1) Should be Unique and not null.
2) Mainly used for Referential Integrity.
3) While creating table only primary key is mentioned and there is no primary index mentioned .Instead of first column the primary key column will be taken as unique Index.


Primary Index:
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1) Could be Unique or Non Unique
2) Mainly used for Data Distribution and Data retrieval in Teradata.
3) Null values are allowed
4) Choosing wrong primary index leads to data skew/Amp Skew.