S sc=##class(%SYSTEM.SQLGateway).TestConnection(CONNECTIONNAME,,,.err)
Connection successful
zw sc,err
sc=1
err=""

Success on testing, but failes on "GetConnection":

 $$$ThrowOnError(sqlgatewayconnection.GetConnection(connectionname,10))

ERROR #6022: Gateway failed: GetConnection.

w ##class(%SYSTEM.SQLGateway).GetJDBCConnection(connectionname)0