EM 12c/EM 13c monitoring credentials for the database in Enterprise Manager password has expired/account locked

Issue:

ORA-28001: the password has expired The Connect Descriptor was (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = <hostname>)(PORT = 1521))(CONNECT_DATA = (SID = <sid>)))

The error message shown above indicates that the agent is unable to monitor this database because the agent cannot logon. 
To correct this, the Monitor Password needs to match the corresponding database password for dbsnmp. 
To change both the dbsnmp database password and the Monitor Password, click the Change dbsnmp Password button. 
This operation will also unlock the dbsnmp user.

Cause:

The dbsnmp password has expired" or "ORA-28000: the account is locked"

Solution:

Method 1 -

SQL> select username, account_status from dba_users where username=’DBSNMP’;

USERNAME   ACCOUNT_STATUS
__________________________

DBSNMP       EXPIRED

SQL> alter user dbsnmp identified by <password> account unlock;

User altered.

update dbsnmp password in OEM grid control.

Method 2 -

1. Login grid control with sysman
2. Click Setup -> Manage Cloud Control -> Agents
3. Click Server name
4. Goto Monitoring -> Click Database Instance name
5. Click configure and Provide sys password
6. Change password

7. Click test connection
8. Message displays “The connection test was successful”
9. Click next
10.Submit