How to modify ASM diskgroup redundancy to external.

Steps to convert the asm disk group redundancy from normal to external

DB:
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shutdown immediate;

startup mount;

backup device type disk format '/u01/app/orascp/rman_backup/archivelog/%U' archivelog all;

backup device type disk format '/u01/app/orascp/rman_backup/%U' database ;

create pfile='/u01/app/orascp/rman_backup/initcastrop.ora' from spfile;

alter database backup controlfile to '/u01/app/orascp/rman_backup/control.ctl';

shutdown immediate;

Login to ASM as Oragrid
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sqlplus "/ as sysasm"

drop diskgroup ORADATA including contents;

shutdown immediate;                (ASM)

startup nomount;

create diskgroup ORADATA external redundancy disk 'ORCL:ORADATA1' SIZE 51199M ,'ORCL:ORADATA2' SIZE 51199M ,'ORCL:ORADATA3' SIZE 51199M , 'ORCL:ORADATA4' SIZE 51199M;

----Alter diskgroup ORADATA mount;

shutdown immediate;

startup;


Login to RDBMS as orascp
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startup nomount pfile='/u01/app/orascp/rman_backup/initcagssp.ora'

create spfile='+ORADATA/castrop/spfilecastrop.ora' from pfile='/u01/app/orascp/rman_backup/initcastrop.ora';

rman target /

restore controlfile from '/u01/app/orascp/rman_backup/control.ctl';

alter database mount;

restore database;

recover database;

alter database open resetlogs;