Execution Steps in Transformer Stage

I've been asked this questions so many times in interviews and by different practitioner also that What are the data processing steps when datastage is processing transformer, So here I tried to compiled. Have a look -


To write efficient Transformer stage derivations, it helps to understand what items get evaluated and when.

Evaluate each stage variable initial value
For each input row to process:
   Evaluate each stage variable derivation value, unless
   the derivation is empty
   For each output link:
      Evaluate constraint, if true:
         Evaluate each column derivation value
         Write the output row
   Next output link
Next input row

The evaluation sequence for a Transformer stage that has a loop condition defined is:

Evaluate each stage variable initial value
For each input row to process:
   Evaluate each stage variable derivation value (unless empty)
   Evaluate each loop variable initial value
   While the evaluated loop condition is true:
         Evaluate each loop variable derivation value (unless empty)
         For each output link:
            Evaluate constraint, if true:
               Evaluate each column derivation value
               Write the output row
         Next output link
   Loop back to While
Next input row

The stage variables, loop variables, and the columns within a link are evaluated in the order in which they are displayed on the parallel job canvas. Similarly, the output links are also evaluated in the order in which they are displayed.

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