ORA-32017: failure in updating SPFILE, followed by: ORA-65500: could not modify DB_UNIQUE_NAME, resource exists (12c)

I was working to setup a Data Guard in my test machine and noticed the following  error when I was trying to change the db_unique_name parameter in the primary database -

 SQL> alter system set db_unique_name=TESTPR scope=spfile sid='*';  
 alter system set db_unique_name=TESTPR scope=spfile  
 *  
 ERROR at line 1:  
 ORA-32017: failure in updating SPFILE  
 ORA-65500: could not modify DB_UNIQUE_NAME, resource exists  

It looks like that 12c CRS now prevents modification of database parameters with respect to it's  configuration protection.

So, I had to do the followings to workaround this -

 -- Stop and remove the database from CRS   
 # srvctl stop database -d TEST   
 # srvctl remove database -d TEST  

 -- Add the parameter (Now it will work)  
 SQL> alter system set db_unique_name=TESTPR scope=spfile sid='*';   
 System altered.   

 -- Add the database back into the CRS   
 # srvctl add database -d TESTPR -n TEST -o /u01/app/oracle/product/12.1.0.2/dbhome_1 -p +DATA/TEST/PARAMETERFILE/spfile.266.897146761 -r PRIMARY -a DATA,RECO  

So, it's best to either set the db_unique_name during the database creation or if it's required to change on a later date, then consider the above workaround.