Updation of sales order after varaint tables

Hi

we create sales order with variant configuration values fetching from variant table.

After updating saved the sales order.

Now we used to update one variant table .related to the above sales order using ABAP development. The ABAP development is working fine. Variant table is updating correctly.

But after updation of variant table the relevant variant table values are disappearing and after some time its updating.

Why the system is taking so much time for updating the sales order from variant table.

How to fix it, please suggest