The Unix shutdown kills the Sybase process (on the syslogs, this is like a shutdown with nowait).
The worst case can be a really long recovery process during the restart of the ASE... and a big jump in your identity values ;-)
After this crash, we started having problems with sybase, like it becomes unusually slow after every 7-8 days. If we do shut down, it is fine. But after few days, it again becomes very slow. What could be the reason? Is it possible that some tables may be corrupted?