Performance issue on update Step- Prepare for index creation SIA

Hi,

We upgrade from siebel7.7 SEA -> 8.1.1.5 SEA-> 8.1.1.10 SIA, and we've finished phase 1 upgade, and now we are upgrading from 8.1.1.5 SEA t 8.1.1.10 SIA.

And at first serveral steps, we are ok, but when we run into Prepare for index creation SIA steps, i can see a lot of update or insert DML operation runs, most of them has very bad performance.

One of worst one took 6 hours but still running. And from the plan, it run many full scan, and we have very huge table, like S_EVT_ACT, S_ORG_EXT, etc. So if full scan those tables, it will be a pain.