A_MSSQL_DEFAULT_CONNECTION specifies the name of the server to which the run time system connects. If A_MSSQL_DEFAULT_CONNECTION is set, the server is named localhost. To reference tables in another server, open the file servername.database.owner.table.
Example
Suppose you have two servers, one named TOM and one named HARRY. If most of the tables you want to access are on the server HARRY, you should set:
A_MSSQL_DEFAULT_CONNECTION HARRY
For those occasions when you want to access the TOM server, you could open the file this way:
TOM.stores.johndoe.purch1