Oracle LGWR is not running at highest priority

The Oracle database does automatically increase the priority on Solaris if you run
the database version 11.2.0.4 or later. On older versions this does not happen.

If you are on Oracle 12.1.0.2 it could be because of Bug
27092821 - IN 12C CRITICAL DATABASE PROCESSES ARE NOT RUNNING WITH HIGHER PRIORITIES IN FSS
It is fixed in 12.1.0.2.99

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