Database Reference
In-Depth Information
When you run the file for the month of
JAN
, the Aggregator transformation will calculate
the value of three records and give the corresponding output, which is 6000 in our case.
When you do not check the
Incremental Aggregation
option, Informatica again calcu-
lates the six records in the file for the month of
FEB
and gives you the result, which is
9000 in our case. If you use the
Incremental Aggregation
option, the aggregator cache
will save the value of the last run, which is 6000. When you run the same process for the
month of
FEB
, Informatica replaces the first three records of the file with the value stored
in the cache and adds new records to get the result. This results in faster calculation, as the
number of records to be calculated reduces.
The basic criterion in order to use incremental aggregation is that the data from the previ-
ous run should remain the same.
If the records from the previous run change, the result will be incorrect, as Informatica
will not consider the changed value and will replace that value with the value stored in the
cache. To handle this, make sure that you check the
Reinitialize aggregate cache
box.
When you check this option, Informatica reinitializes the aggregate cache value and stores
the new value. It is important to note that you need to uncheck the
Reinitialize aggregate
cache
option if your data is not changing, otherwise it will always keep on reinitializing
the cache, which will indirectly hamper the performance.
