ASM system administrator credentials are stored into the sys_admin_login table of the ASM database, into the row having sal_key = 1. System administrator username is stored into the sal_login field, while the password is stored into the sal_password field. Password is encrypted by MD5 so, it's not possible to "read" old password into the database directly, however it's simple to reset it.
Executing this SQL query on ASM database:
UPDATE sys_admin_login
SET sal_password = '73acd9a5972130b75066c82595a1fae3'
WHERE sal_key = 1
GO
you can set ASM system administrator password to "admin" (without double quotes).
