Here we will see how DAC
loads the data using the execution plan into target tables.When you run an
execution plan, data is extracted from one or more tables in the source system
database, dumped into staging tables, and then loaded into tables in the data warehouse.
The DAC supports the following extract and load combinations:
Full Load:
Here DAC does full extract
of data from the source. All data is extracted from the source system and
loaded into the data warehouse. The DAC performs a full extract for a task if
the source and staging tables have null refresh dates. If the staging and
target has null refresh dates then full load of data is done from staging to target.
Its Just a full extract and full load
Full Extract and Incremental Load
Here as we said above the
Full extract process is same i.e the whole data from source is loaded into the
staging .In this case the source or staging table is null, the DAC invokes the
full extract workflow.
Data is loaded from the
staging table into the target table through an incremental load command. When
the staging and target tables have refresh dates(incremental dates), the DAC
invokes an incremental load command. This happens when data is loaded from new
source
The incremental load
process requires additional logic to determine whether a record should be
inserted or updated which is done by the ETL part Therefore, if you add a new
source connection to populate an existing data warehouse, you should expect the
incremental load to be slower than when running a full load.
Incremental extract And Incremental Load
Here new or changed records
are extracted from the source system by DAC and loaded into the data warehouse.
Now DAC decides whether the records needs to be updated or inserted based on
the incremental logic.The DAC performs an incremental extract for a task if the
source and staging tables have refresh dates and performs an incremental load
for a task if the staging and target table have refresh dates.
Read about Dac In Obia
Read about Dac In Obia
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