A_MSSQL_LOGIN indicates the user name under which you want to connect to the database system.
Example
To connect to the database with the user name MYNAME, you would specify:
A_MSSQL_LOGIN MYNAME
in the runtime configuration file.
If A_MSSQL_LOGIN is not set, the runtime will use the value of your USER environment variable as your Microsoft SQL Server login name. For this automatic login to succeed, you must have set up a user with the same name as your computer login name.
See also
A_MSSQL_PASSWD runtime configuration file variable
Section B.2.3, "Acu4GL for Microsoft SQL Server: Setting Up a User Account"