some permission have changed between 11 and 12, before creating a 11 database in an 12 grid environment some permission have to be changed:

./crsctl modify type ora.database.type -attr "ATTRIBUTE=TYPE_ACL, DEFAULT_VALUE='owner:root:rwx,pgrp:dba:rwx,other::r--,group:dba:r-x,user:oracle:rwx'"

./crsctl modify type ora.service.type  -attr "ATTRIBUTE=TYPE_ACL, DEFAULT_VALUE='owner:root:rwx,pgrp:dba:rwx,other::r--,group:dba:r-x,user:oracle:rwx'"

otherwise you will get an permission error when the database will be added to the grid.

if you already got the error while creating the database with dbca then you can add the database manually to the grid, but you have to use srvctl from the 11 home directory:

/home/app/product/11.2.0/dbhome/bin/srvctl add database -d <DB> -o /home/app/product/11.2.0/dbhome

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