A-MSSQL-DEFAULT-CONNECTION is the name of the server to which the runtime will connect. This variable is checked only if the DSQUERY environment variable has not been set. If neither DSQUERY nor A-MSSQL-DEFAULT-CONNECTION is set, the server is named DSQUERY, just as for ISQL. 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, then 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
See also
The Microsoft SQL Server documentation on ISQL.