How ASM instance reads initiator parameter file on ASM disk when startup?

As is known,ASM instance need to read initiator parameter file when startup.However,the diskgroups are not mounted at that time.How does ASM instance read it?

Oracle ASM uses registry to locate initiator parameter file.The file records oracle registry information is '/etc/oracle/olr.loc'.It indicates the directory of oracle registry,namely '$ORACLE_HOME/cdata/localhost'.User can dump oracle registry contents by using 'dumpocr -local -xml'.In a result,'OCRDUMPXML' is generated in that directory,which can be read by vi editor.Then user can find entry about location of 'asmparameter',such as '+data/asm/asmparameterfile/spfile.266.845133178'.So even you generate pfile from spfile in ASM instance,it doesn't take effect,because ASM instance reads spfile still.

A:

All information about ASM parameterfile is in the header of disks.

That's a demonstration：

http://oracleinaction.com/asm-spfile-on-asm/