spnego/construct_SNC_name is a SAP Parameter attribute which is used to control Construct SNC name for given Kerberos User Name 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 .
During SPNego authentication the determined Kerberos User Name
(consisting of two parts: user name part and domain part, separated by
the @ sign) needs to be converted into a SNC name in order to utilize
the existing SNC mappings.
This approach is applicable to all Kerberos-based SNC products.
Unfortunately, the SNC products differ in the way how they construct a
SNC name for a given Kerberos User Name. This profile parameter allows
to configure the construction rules.
The default value is suitable for the usage of the product SAP NetWeaver
Single Sign-On as
See SAP Parameter Documentation for full SAP documentation for this profile parameter.