ETL，etl是什麼

ETL，etl是什麼

SDE: Source Dependent Extract

SDE mappings -- extracts the data from the transactional Source System and loads into the data warehouse staging tables.

SDE mappings are designed with respect to the source's  unique data model.

SDE_* workflows have only the staging table, the workflow will load the data into the staging area tables.

In the staging the tables will not have index.

It always truncates the data and loads the data into staging table.

So the load type will be BULK mode because the stagings have no indexes defined.

SIL: Source Independent Load

SIL mapping typically select from the staging tables and load the target warehouse tables.

SIL_*  --  You can find two SIL_* workflows in the Workflow Manager.

During a full load the workflow (SIL_*_Full) will be invoked from DAC and the target table is truncate, indexes are dropped, data is loaded in 'Bulk' mode and then the indexes are rebuild.

Durring incremental load , the workflow (SIL_*) will be invoked which would just insert/update the incremental data. Since the amount of data during incremental load is minimal compared to full load this would run in 'Normal' mode.If indexes are present on a table "BULK" mode does not work.