Best way to extract data when source system tables don't have a last modified date
I am working on creating a datamart and some of the big tables from oracle source system doesn't have last updated column. I am planning to extract full load to staging area which is on SQL server 2012 . So i will be deleting data from target before re-load in every run. The 4 tables in question from source system have 18.3 , 9.6 ,19.89 and 206 million records. I ran the job today , which has around 23 dataflow consisting of small and huge tables. My staging job is still running , its been more than 3 hours and i am anticipating it will run for 1-2 hours more.
Any suggestion on how to handle this scenario wherein im doing a full refresh of staging tables. I am afraid, if the simple extraction is taking a long time, how the performance will be when i will actually be doing transform and building dimensions and facts.