inter instance parameter values communication

Assume that spfile is not the same for both instances in rac .like spfile_inst1 and spfile_inst2 for 2 instances of the database.

Now If I try to do osmething like below:

SQL> startup mount

ORACLE instance started.

Total System Global Area 1085640704 bytes

Fixed Size                  2220680 bytes

Variable Size             520097144 bytes

Database Buffers          553648128 bytes

Redo Buffers                9674752 bytes

ORA-01105: mount is incompatible with mounts by other instances

ORA-01677: standby file name convert parameters differ from other instance

how does one instance come to know that what's the parameter value set in other instance?  Which process does all this?

Best regards,

Vishal