To change the ASM SYS Password
Things tried:
SQL> password
Changing password for SYS
Old password:
New password:
Retype new password:
ERROR:
ORA-00600: internal error code, arguments: [15051], [], [], [], [], [], [], []

SQL> select INSTANCE_NAME from v$instance;

INSTANCE_NAME
—————-
+ASM

SQL> ALTER USER sys IDENTIFIED BY <new_password> REPLACE <old_password>;
ALTER USER sys IDENTIFIED BY <new_password> REPLACE <old_password>
*
ERROR at line 1:
ORA-01109: database not open

The following error also might occur:
SQL> alter user sys identified by ;
alter user sys identified by
*
ERROR at line 1:
ORA-01031: insufficient privileges

Solution
We can not change the password for ASM databases via alter user command.
The password should be the one provided when the password file was created,also REMOTE_LOGIN_PASSWORDFILE should be set to EXCLUSIVE on all instances.

If you want to change the password then you would need to recreate the password file using the orapwd utility
Recreate the password file for the ASM instance as follows:
1.   Set the ORACLE_HOME and ORACLE_SID to the ASM instance
2.  connect /as sysdba from sqlplus
3.  If the value of the “remote_login_passwordfile” parameter in the pfile or spfile is EXCLUSIVE, you must shutdown your instance
4.  RENAME or DELETE the existing password file PWD<SID>. ora( In Windows) / orapw<SID> ( in UNIX)
5.  Issue the command:
WINDOWS:
orapwd file=<ORACLE_HOME>/database/PWD<SID>. ora password=<sys_password>

UNIX:
orapwd file=<ORACLE_HOME>/dbs/PWD<SID> password=<sys_password>

The passwordfile can be recreated for ASM while ASM instance is up. Usually for normal DB instances, we recommended that DB instances be shutdown before changing the passwordfile.