Oracle's password requirements include the following:
Passwords must be at least 6 characters long.
They must contain a mix of alphabetic and numeric characters.
Passwords cannot match or be a reverse of the username.
They should not have too many repeated characters.
Recently used passwords cannot be reused.
Oracle recommends you avoid certain special characters, including:
Quotation marks: " "
Ampersand: &
Asterisk: *
Vertical bar: |
Percent sign: %
Tilde: ~
Backslash: \
Dollar sign: $
Pound sign: £
At sign: @
Forward slash: /