This article discusses the data source's Test Connection button.

If my data source's Test Connection button works, does it guarantee that my queries will reach the back end server?

For an RDBMS data source (e.g. Oracle, Microsoft SQL Server, or Sybase):
If the Test Connection button works, it means that the TIBCO Data Virtualization server verified that a JDBC connection could be opened to the back end database server. In this case, yes, queries will reach the server.

For non-RDBMS data sources (e.g. LDAP):
When you click the Test Connection button, TDV pings the computer on which the back end server is running. TDV does not attempt to actually connect to the server (as it does for RDBMS data sources). In view of this, a successful outcome from the Test Connection button does not guarantee that queries will reach the server. What it means is that TDV verified the machine to be reachable over the network. In the case of the machine being reachable over the network, but the back end server being unresponsive, queries will not be executed.