login/password_downwards_compatibility is a SAP Parameter attribute which is used to control password downwards compatibility (8 / 40 characters, case-sensitivity) information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
As of SAP NetWeaver (SAP_BASIS) 7.0, the system supports logon with
passwords that can consist of up to 40 characters (previously: 8), and
which are case-sensitive (previously, the system automatically converted
from lowercase to uppercase letters). It is also possible to use any
Unicode characters.
Unfortunately, this change is not backward compatible. The passwords are
stored as hash values that are not backward compatible. If you are using
this system together with other systems that only support backward
compatible password hash values, you need to react appropriately.
The values of this profile parameter specify the desired behavior
(default value = 1):
0 : No backward compatibility; the system only generates new password
hash values (which are not backward compatible).
1 : The system also generates backward compatible password hash values
internally, but does not evaluate these for logons (to the local system)
with passwords; this setting is necessary if this system is used as a
central system of a Central User Administration, and systems that only
support backward compatible password hash values are connected to the
system group.
2: The system also generates backward compatible password hash values
internally and evaluates these if a logon with a password that is not
backward compatible fails, to check whether the logon with the backward
compatible password (truncated after 8 characters and converted to
uppercase letters) would have been accepted. This is logged in the
system log; the logon fails. (This setting identifies backward
incompatibility problems.)
3 : As with 2, but the logon is regarded as successful (avoidance of
backward incompatibility problems).
4 : As with 3, but no system log entry is written.
5 : System only issues backward compatible passwords hash values.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.