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 database. So during migration of code between environments the sequence has to be reset manually. Bigger problem arise when the tables with data is brought from production environment to QA environment; the mapping cannot be immediately run because the sequences are out of sync.

2. Sequences belong to the target schema and the database and do not belong to the processes as the table object should define & hold values for the attributes and not something external to the system.

3. At first it might seem that Sybase/SQL server does not support sequences but checkout the post & that will solve the problem.

4. Logically it seems that Informatica calls to oracle procedure will slowdown the ETL process but in real world, I have found it not to be true. Additionally this process is only called when a new reference data/Dimension is added. New reference data is not as volatile as transactions; so the adverse effect is nullified.

5. If Identity columns are used instead, it causes more problems as you loose programmatic control on it. Example any type II dimension changes are become a nightmare to manage.


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