Is there any way to optimize RMA performance? It becomes slow when I upload more than 75,000 rows DTAB.

Do you have pagination set for the decision table? Check Developing Rule Maintenance Applications in the documentation, Chapter 6 on Template Displays, Specifying Displays for Decision Tables. If you have an older code base, you might not have pagination set, and the documentation will explain how to set it up, and the fewer rows you show per page, the more it can help your RMA performance in showing those rows.