Can't create diskgroup in Oracle 19c I've successfully installed Oracle 19c with this article.
Now I need to restore the database from existing backups. I've first restored the control file, then I started to restore the database:
rman&gt; restore database;
...
ORA-19504: failed to create file &quot;+DATA&quot;
ORA-17502: ksfdcre:4 Failed to create file +DATA
ORA-15001: diskgroup &quot;DATA&quot; does not exist or is not mounted
ORA-15374: invalid cluster configuration
...

Then I tried to create the diskgroup, and it failed:
SQL&gt; create diskgroup DATA external redundancy disk '/dev/loop1' force;
create diskgroup DATA external redundancy disk '/dev/loop1' force
*
ERROR at line 1:
ORA-15000: command disallowed by current instance type

Is there a work around? I can either ignore the diskgroup or find a way to create one, I just don't how to fix it.
It seems you are in RDBMS instance
to check use the following query:
select value from v$parameter where upper(name) = 'INSTANCE_TYPE';

or
show parameters instance_type

If you get RDBMS value, go to operational system shell and check the SID of ASM instance in /etc/oratab
cat /etc/oratab

After cat the file, you will get something like it:
+ASM:/u01/app/19.0.0/grid:N

The rows are delimited by :. The first field is the SID (in my case +ASM), the second field is the GRID_HOME (also ORACLE_HOME)
You can use oraenv to set the variables needed to access the ASM instance or you can set the variables manually with export command.
With oraenv:
. oraenv

after issuing the . oraenv command, type your SID
or export the variables manually
export ORACLE_SID=+ASM
export ORACLE_HOME=/u01/app/19.0.0/grid
export PATH=$ORACLE_HOME/bin:$PATH

NOTE: to create asm diskgroup you need access the instance with sysasm role
sqlplus / as sysasm