Oracle ASM Diskgroup Attributes Impact

I had an environment where I need to change the ASM diskgroup access_control.enabled to True for testmaster setup for thin clones. So question is 

• If I change this Attribute for DATA diskgroup, Oracle manual says will not impact existing ASM files. What will happen to the new file created keeping in mind that there is only one user named ORACLE that owns all ASM/GI/RDBMS software on the system?  Do I need to be careful in setting ASM attribute umask ?
• Also testmaster setup runs the commands like below where it is adding the Group also. So how this new group can impact all other new files added to already running regular database and using the Diskgroup? Do I need to be careful in defining this new Group in ASM? 

ALTER DISKGROUP <diskgroup> ADD USERGROUP '<Group Provided in OEM Screen>';

ALTER DISKGROUP <diskgroup> SET OWNERSHIP OWNER='<OSOWNER>',GROUP='<GroupAddedAbove>' for file '<ASM Full File Path>';

ALTER DISKGROUP <diskgroup> SET PERMISSION OWNER=read only,GROUP=read only for file '<ASM Full File Path>';     

• Without setting these permission, Thin clone will fail to create the clone. Don;t have any environment to play and so if someone can share their experience 

TxSanjay

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