Slower Development Databases and Servers

It is a normal trend in it to buy the most powerful machine for production usage. Example you production database box will have 16 CPUs your QA 8 and your Development box 4 or 6. Similar ratio is maintained on ETL servers, Application servers, and Hard Disk performance. Logic being the production environment is critical […]

Informatica interview questions & FAQs

What is a source qualifier? What is a surrogate key? What is difference between Mapplet and reusable transformation? What is DTM session? What is a Mapplet? What is a look up function? What is default transformation for the look up function? What is difference between a connected look up and unconnected look up? What is […]

Loading & testing fact/transactional/balances (data), which is valid between dates!

This is going to be a very interesting topic for ETL & Data modelers who design processes/tables to load fact or transactional data which keeps on changing between dates. ex: prices of shares, Company ratings, etc. The table above shows an entity in the source system that contains time variant values but they don’t change […]

What ETL performance (processing speed) is good enough?

Every ETL developer / Data Warehouse Manager wants to know if the ETL processing speed  (Usually measured in NUMBER OF ROWS PROCESSED PER SECOND on target side)is good enough? What is the industry standard? I can give a politically correct answer like… Well it depends…  But I would rather be blunt and say that usually […]

Why Informatica sequences & Sybase/SQL server identity columns, should not be used?

Informatica provides the sequence object to create surrogate keys during load. These object is also sharable within various mappings hence can be used in parallel. But I will recommend never using it.  Here’s the Reason why…. 1. MIGRATION ISSUE:  The sequence is stored in the Informatica repository. That means it is disconnected from the target […]

Simulating Oracle Sequences in Sybase & SQL Server

Programmatic control is lost when identity columns are used in Sybase and SQL Server. I do not recommend using Identity columns to create surrogate keys during ETL process. There are many more reasons for that. Oracle has the sequence feature which is used extensively by Oracle programmers. I have no clue why other vendors are […]