after EBS 11i DB upgrade from 9i to 10g R2 10.2.0.5 retropay rollback hangs until killed on OS

Hi everybody

I have been looping around my self for more than one week now without any solution.

First of all my environment is

OS IBM AIX 6.1

DB was 9i then upgraded to 10.2.0.5 ( another test on 10.2.0.3 with same issue)

EBS 11i 11.5.10.2

after upgrading the database our HR consultant was testing the instance and faced some problems with performance when running payrole request and editing init.ora solved it by adding

_optimizer_cost_based_transformation = off

_optimizer_push_pred_cost_based = false

_gby_hash_aggregation_enabled = FALSE

optimizer_index_cost_adj = 50

optimizer_index_caching = 0

after that rolling back the payroll (retropay) hanged for a long time, terminating the request didn't kill the process so I had to kill it from OS