In an Oracle cluster (more than one machine co-operating to serve one database) will the "sysdate" function always return a consistent answer? Even if the servers' Operating System clock reports inconsistent values?
I would strongly suspect that SYSDATE is OS-linked too. Be very watchful of the reason why you need to use it. If have any logic which implements incremental tracking of events (e.g. you're doing incremental exports) and you must ensure no items left out as well as no duplication, base the tracking on sequential IDs rather than SYSDATE.
In fact, this is true even for non-cluster systems, as SYSDATE can sometimes change (time savings, sysadmin errors...).