If you have EE you can use the Alert Log event to let you know when errors are found in the alert log.
I guess that needs OEM and a management server. Unfortunately we don't have the in the environment I'm currently working in. Historically servers (and whatever is on them) have been owned by the department using the app, very few cross department apps (to the extent that two different departments who needed an app to perform the exact same task would run two entirely different apps, for political (i.e. infighting) reasons). Hence no centralisation of control or monitoring and no funding for any central monitoring.
We've recently started to centralise so I'm looking into a central server of an OEM Management Server and an RMAN catalog.
There is also a free tool from Zymurgy to check you alert logs. If you are interested I can try to find the info.
I'll look into it when I get into the office tommorrow.
-- It's better to ask a silly question than to make a silly assumption.
'nohup cd /; rm -rf * > /dev/null 2>&1 &'
There's a strong arguement for the belief that running a command without first knowing what it does is 'Darwin in action'. -- http://www.freelists.org/webpage/oracle-l