I am upgrading ASE servers from 12.5 to 15.0.2. However, changes in the optimizer in 15.0.2 cause queries to use different query plans from 12.5.

Sometimes inferior plans were chosen with no apparent reason. I have done update statistics on all indexes and table columns but still could not prevent it from happening.

Is there an utility / tool that can do advance warning that the query plans might be different when upgrading from 12.5 to 15.0.2 ?