RAC file system confusing?

Shared file between RAC DB Instances:

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>>> Below are the list of files which are shared between RAC cluster instances and each cluster instances can read and write same file.

>>> These are the single set of files and not instance specific files.

a. spfile ------- On ASM

b. controlfile ------- On ASM

c. system ------- On ASM

d. sysaux ------- On ASM

e. users... etc ------- On ASM

f. tempfile ------- On ASM

g. password file  ------- On ASM

Non-Shared file between RAC DB Instances or Each Instance specifi files:

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>>> Below are the list of files which are non-shared between RAC cluster instances and each cluster instances can read the files but can not write same file.  

>>> These are instance specific files in RAC cluster.

a. undo (undo1 & undo2) ------- On ASM

b. redo group ------- On ASM

c. pfile ------- FS (OS storage) / SAN /NAS /NFS 

Each Instance specific files:  

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>>>These are instance specific files in RAC cluster.

a. alert log ------- FS (OS storage) / SAN / NAS /NFS 

b. trace ------- FS (OS storage) / SAN / NAS /NFS 

c. trm ------- FS (OS storage) / SAN / NAS /NFS 

d. incident files ------- FS (OS storage) / SAN / NAS /NFS 

e. core dump ------- FS (OS storage) / SAN / NAS /NFS 

etc...

Regards,

Mallik