Is I understand it, you store data with no aspect of keeping historical values, but wish to keep track on when the record was originally created, and last update time? In this, I think you have to extract the Sys_create_date from the existing target table. This could be done in a previous job, if don't wish have duplicate metadata objects for the same physical table. If your target table is indexed properly, this should not be a big performance issue, unless if you update a considerable part of the data.
A different approach is to keep track of the historical values in your DW, which use to be considered as best practice. By doing so, the SCD Type 2 Loader will do "everything" for you... The result is a target table with multiple entries for your business key (optional the surrogate key as well) with a time interval that specifies when in time this record is considered as valid. The current valid record has a high-date, the default for DI Studio is 01Jan5999.
/Linus
Data never sleeps