I am going to change some parameters on primary database (db cache, java pool etc.). I am not sure, if the changes are automaticallly propagated to standby or if I have to make the changes manually on stanby site too? I couldn't find clear answer in documentation. Can you explain please how parameter changes work in dg physical configuration?
if you do some alter system set command on your primary only this database will be changed. You have to do the some changes on your standby. Becuase this changes are made in the spfile and not in the redo stream they will not be send to the standby.
Hope this helps
What I would do on the Standby is create a new pfile from spfile. The I would make the changes you desire in the new pfile.
Then stop apply on the standby and shutdown the database.
Start the standby NOMOUNT on the changed pfile and create a new spfile form it.
The shutdown and start apply again.
If you are using Data Guard Broker consider a different plan.