When there are multiple GN4 installations on the same server, you must install a separate Back4 service for each GN4 'instance'. Multiple GN4 installations on the same server means each installation has a separate database, application directories, virtual directories, appsettings.xml, etc.  This is the case, for example, when multiple GNPortal systems are hosted on the same server.

There will be one installed 'instance' of Back4 for each GN4 installation. Since each Back4 instance reads a separate database, it follows that each instance has its own Back4 configuration.

When installing multiple GN4 instances on the same server, modify each appsetting file to include the instance name for that GN4 installation. The instance name is defined by adding the key ‘Db.Instance’ to the appSettings section of the configuration files (Web.config, Back4.exe.config etc., or more likely in the single appSettings.xml file that is referenced by each of those configuration files)
 
The value of the Db.Instance setting is used to compose the name of the Back4 service and all of the Windows event logs used by the system. For example, if appSettings.xml contains:

<add key="Db.Instance" value="GNPortal_Site1" />

the Back4 service will be called 'Tera Back4 - GNPortal_Site1' and the Windows Back4 event log will be called 'TeraGN4 - GNPortal_Site1'.
 
NOTES:

•Db.Instance should be set BEFORE installing Back4, and should not be changed before uninstalling it.

•If Db.Instance is missing or empty, there is only a single instance of the Back4 and Windows logs.

See Also

Configuring Back4

Install options