Performance issue in SAPDBDDF after migration to SYBASE ASE16 02 05

Hi we have done a mock migration of our productive ERP system from Aix/DB2 9.7 to Suze 12/ ASE16 02 05. We have followed the best practice guide and configured the system as recommended. After migration we are noticing that in the migrated system , transaction FBL5n which uses the logical database DDF is doing a very slow sequential read on BSID . The SQL statement has no where clause and the time taken is almost 4 times that of the system running on DB2. Is there any specific step which needs to be executed to handle this ? The client refuses to go live on the new platform unless there is a solution to this . Any clue will be highly appreciated .

Regards

Sid