The Oracle database does
automatically increase the priority on Solaris if you run
the database version 126.96.36.199 or later. On older versions this does not happen.
If you run the Oracle database in a Solaris Zone, make sure you have 'proc_priocntl' set in limitpriv in your zonecfg. This is required to allow the change of the priority inside the zone.
Ideally the ora_lwgr_x
process should run in the FX class with prio 60.
This can be verified using
ps -efcZ | grep lgwr