It differs from other conventional database systems from its architecture to the processing speed. Easy scalability and its fault tolerance keep the demand high for this system.
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3. AMP (Access Module Processor) : AMP is the heart of Teradata which does most of the operations for data storage and retrieval. It also takes care of finding the rows requested, Lock management of the tables and rows, Sorting rows, Aggregating columns, Join processing etc.
Primary Key is a concept that uniquely identifies a particular row of a table.
Care should be taken while choosing a NUPI so that the distribution of data is almost even . UPI/NUPI decision should be taken based on the data and its usage.
It is not a wise decision to choose DEPTID as the PI of the employee table. Reason being, employee table will have thousands of employees whereas number of departments in a company will be less than 100. So choosing EMPID will have better performance in terms of distribution.
Both UPI and NUPI is always a One AMP operation as the same values will be stores in same
Because this is a Primary Index access operation, the PE knows this is a one AMP operation. The PE hashes 100 and the Row Hash points to a bucket in the Hash Map that represents AMP X. AMP X is sent a message to get the Row Hash and make sure it’s EMP 100.
• Joining tables
The PE will direct the chosen AMP to look-up the Row Hash in the Subtable. The AMP will check to see if the Row Hash exists in the Subtable and double check the subtable row with the actual secondary index value. Then, the AMP will pass the Primary Index Row ID back up the BYNET network. This request is directed to the AMP with the base table row, which is then easily retrieved.
• If the rows to be joined are not on the same AMP, Teradata will either redistribute the data or duplicate the data in spool to make that happen.