Informatica Variables are crazy

I really have to say the idea of the Informatica mapping variables is crazy.

In case of using the mapping variables to pass information among sessions, it must be first overridden with the smallest value (or largest value) in the “pre-session variable assignment”. It is because the “post-session variable assignment” retrieve the saved value (persistent value). Here is the steps:

1. use the parameter file or the “pre-session variable assignment” override the mapping variable; otherwise the initial value will be the persistent value saved in the repository;
2. use the SETVARIABLE function in the mapping to change the mapping variable;
3. “At the end of a successful session, the PowerCenter Integration Service compares the final current value of the variable to the start value of the variable. Based on the aggregate type of the variable, it saves a final current value to the repository.” The aggregate type is either MIN or MAX.
4. “post-session variable assignment” retrieve the saved value;

The mapping variable is the definition. The session variable is the object during the session. The persistent value saved in the repository is value of each session.

http://datawarehouse.ittoolbox.com/groups/technical-functional/informatica-l/problems-with-setvariable-3283342

The is Sukumar’s comment

Workflow Variable:

The Integration Service looks for the start value of a variable in the following order:

1. Value in parameter file
2. Value saved in the repository (if the variable is persistent)
3. User-specified default value
4. Datatype default value

Mapping Variable :

The Integration Service saves the latest value of a mapping variable to the repository at the end of each successful session. During the next session run, it evaluates all references to the mapping variable to the saved value. You can override a saved value with the parameter file. You can also clear all saved values for the session in the Workflow Manager.

The Integration Service looks for the start value in the following order:

1. Value in parameter file
2. Value in pre-session variable assignment
3. Value saved in the repository
4. Initial value
5. Datatype default value

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