What are routines? are Transfer/Update rules and routines one and the same?

Routines are like conditions or business rules that could be applied to filter the data while entering the BW system or could be used to apply certain conditions on the info objects itself.

There are 4 types of routines

1. Start routine- Could be used at two levels (transfer rule level and the Update rule level)

This Start routine written at the transfer rule level helps filter the necessary data coming from the source system.
For Example: If you decide to extract data that contain only quantity greater than 500 , then you could specify the Start rouitne to achieve this.

The Start routine at the Update rule level provides similar functionality but at this point it helps direct specific data to 
different data targets.  For Example: If there 3 data targets being fed from the Infosource, you may want to apply some condition to each data target, like send year 2000 data ti Data target1, 2001 to data target 2 and so on.  This can be achieved by using Start routine at the Update rule level

2. Transfer Routine: This feature is available at the transfer rule levels

While performing the transfer rules operation, there are 4 features available to the developers to create business rules on top pf the Infoobjects.

1. You could do a one to one mappping of the Infoobject
2. Provide a constant value
3. Include a formula
4. Write an ABAp routine.

These 4 options refers to the transfer routine

3. Update Routine:
The limitations of just having 4 options in the transfer routine is overcome at the update rule level. There are various other 
sophisticated features avaialable apart from the 4 options mentioned above. These business rules could be specified pertaining to each data target.

4. Conversion Routine: It provides functionality to do Currency and unit conversion.          *-- Suman

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