The connection panel

This panel is what you see once you've launched the Diff and going to start a comparison.  Mostly, it consists of two identical panes, containing the usual SQL Server connection parameters.  Some of the parameters are obvious, but some deserve a comment.

The "Secondary database" selection at the bottom has 3 states:

• "On the same server" means that all server-selection fields in the right-hand connection pane are disabled, so you only need to configure one set of connection parameters and choose two different databases on that server;
• "On a separate server" enables separate server selection in each of the panes;
• "Start with one database" completely turns off the right-hand connection pane, so you only specify one database and the Diff starts in "exploring" mode. In this mode there is no comparison, but you can quickly view the schema and script any parts of it.

Note that the [Compare] button remains disabled until you enter all required connection parameters and specify two different databases (except that for "Start with one DB" mode you obviously only need to choose one). The Diff won't compare a database against itself.

The server selection combobox is pre-filled with known server names fetched from several places:

• From the list of 'preferred servers' which Microsoft tools keep in the registry at "HKCU\Software\Microsoft\Microsoft SQL Server\80\Tools\Client\PrefServers";
• From the list of server aliases you can define in the MS Client Network Utility;
• And from the list of recent server names which the Diff keeps in its own settings.

Note that some of these sources can keep not only a server name itself, but some additional information like the network library required or the port number.  The Diff implements that by keeping a piece of connection string associated with each server name in the combobox.  Therefore when you select a server in the combobox, some other connection parameters may change accordingly.

The Diff doesn't actually look for available SQL servers until you tell it to. There is a button next to the server selection combobox invoking the Server scan dialog dialog, which tries to locate all available SQL servers on the LAN. This dialog is described in more details here. The results of the server scan may be either added to the server combo box or one of the servers may be selected immediately.

The NetLib field: you can usually leave the default value there.  If you do select a specific net library, you must make sure the server name is suitable for it. For example, the usual "Server\Instance" syntax is not valid with the TCP/IP netlib, instead the server name must contain the server IP or name only, whereas the port number determines the server instance.

Note that there are two separate timeout fields: the connect timeout determines how long the Diff will wait when a server connection is being established,  whereas the query timeout specifies how long to wait for a SQL query to return. The default value of 0 means the ADO default timeout will be used (which is normally about 30sec).  To have longer timeouts, you must explicitly specify them, in seconds. The timeout parameters apply to all situations when the Diff accesses the databases:

• Scanning database schemas;
• Executing generated SQL;
• Running  data comparisons.

Persistence

To make using the Diff easier for you, the Diff remembers what you've entered into the connection panel before:

• The list of servers in the server selection combobox;
• The full set of connection parameters of the last comparison you ran.

Besides, you can save any comparison into a file. That saves not only the connection parameters but also a number of other settings.