What are the various methods of getting incremental records or delta records from the ource systems?

getting incremental records from source systems to target can be done
by using incremental aggregation transformation


How can we use mapping variables in Informatica? Where do we use them?

After creating a variable, we can use it in any expression in a mapping or a mapplet. Als they can be used in source qualifier filter, user defined joins or extract overrides and in expression editor of reusable transformations.
Their values can change automatically between sessions.


Do we need an ETL tool? When do we go for the tools in the market?

ETL Tools are meant to extract, transform and load the data into Data Warehouse for decision making. Before the evolution of ETL Tools, the above mentioned ETL process was done manually by using SQL code created by programmers. This task was tedious and cumbersome in many cases since it involved many resources, complex coding and more work hours. On top of it, maintaining the code placed a great challenge among the programmers.

These difficulties are eliminated by ETL Tools since they are very powerful and they offer many advantages in all stages of ETL process starting from extraction, data cleansing, data profiling, transformation, debuggging and loading into data warehouse when compared to the old method.