ORA-15260 error pops up when you try to drop/create an ASM diskgroup while connecting as SYSDBA.

[oracle@node1 scripts]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Wed Jan 26 14:07:43 2022
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL> CREATE DISKGROUP RECO EXTERNAL REDUNDANCY disk '/dev/oracleasm/disks/RECO' NAME RECO;
CREATE DISKGROUP RECO EXTERNAL REDUNDANCY disk '/dev/oracleasm/disks/RECO' NAME RECO
*
ERROR at line 1:
ORA-15260: permission denied on ASM disk group

Oracle 11g onward, oracle requires SYSASM privilege do CREATE or DROP an ASM diskgroup.

[oracle@node1 scripts]$ sqlplus / as sysasm

SQL*Plus: Release 19.0.0.0.0 - Production on Wed Jan 26 14:08:16 2022
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL> CREATE DISKGROUP RECO EXTERNAL REDUNDANCY disk '/dev/oracleasm/disks/RECO' NAME RECO;

Diskgroup created.