DSXchange

I tried to have a good understanding of Run Time Column Propagation (RCP) in term of when and how to use it properly.

Under what circumstances would it be a good idea to enable RCP on the project level?

What are the downside for enabling RCP at the project level.

When not to turn on RCP at the project level.

thanks.

We use RCP to only show columns that have transforms. That way it makes it easier to view. The other columns have not changes and are just passing thru. Much cleaner.

Are there any disadvantages, if we choose RCP in Datastage?

RCP can be confusing at first, since you can do manipulations on columns that don't seem to exist. Along the same lines, you can get confusing warnings in joins when a column is marked as "duplicate" because it is coming from RCP.
In terms of execution and compile times there is no difference.

I agree, it can be confusing.

Most people do not need it because they carry all the columns across manually. Why do they use RCP?

To answer the question as originally asked, IMHO I would never simply turn it on at the Project level unless you had an expert developer team all of whom were very comfortable with it.

The best reason I've seen for RCP is when you have a set of functions (stage types) that you want to use to process a vast set of tables, each that has a different structure ....especially in cases where you don't need "really specific" transformations on certain column names...... Entire generic jobs are written that have no columns at all...... These scenarios may be rare, but it becomes a very powerful option to have a job that works against nearly "any" table.

Ernie

Exactly... turn it on at the job level when you really need or can leverage it properly, case by case. All IMHO, of course.

Hi All,
When i use schema file for reading a data file then i use RCP since i do not want to specify the column names in the source and target.

Regards
Sreeni

I agree with Craig. Turn it on at the job level. I think it helps with shared containers. Only specifying the columns needed.

I've also used it shops with very large structures (for example a record with hundreds and hundreds of columns) where only a few columns needed to be worked on, but all columns needed to be transmitted along to the end result.

I only enable it on a per-job basis - it can cause a lot of problems otherwise.