dbs/db4/ntlogonfile is a SAP Parameter attribute which is used to control Fully qualified name of the file that contains the database logon info 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 .
Application servers on operating systems other than IBM i require a user
and password to establish a database connection. dbs/db4/ntlogonfile
specifies the fully qualified name of the file that contains the user
credentials to connect to the database server. The format has to be
readable by the operating system of the application server in question.
For more information, see SAP note 705886.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.