Loosely coupled tables are created automatically when the data model(3 or More Tables) that includes circular references is loaded into QlikView,to avoid them the circular references create a loop in the QlikView internal logic. These loosely coupled tables need to be handled in order to visualize data in a way that is expected and understandable.
See Article Circular References
Any table can also be made loosely coupled interactively from this dialog or via macros. Additionally, it is possible to declare loosely coupled tables explicitly in the script via the Loosen Table statement.
The normal QlikView associative logic is disconnected internally for loosely coupled tables. This means that selections in one field do not Associate through to the other fields in the table. its very useful to avoid circular references in the data structure in various scenarios. For more examples of how this feature can be used, please refer to the QlikView Reference Manual - Intentionally Creating Loosely Coupled Tables
One or more QlikView internal data tables can be explicitly declared loosely coupled during script execution by using a Loosen Table statement.
The use of one or more Loosen Table statements in the script will make QlikView disregard any setting of tables as loosely coupled made before the script execution.
The syntax is:
Loosen Table tablename [ , tablename2 ...]
Either syntax: Loosen Table and Loosen Tables can be used.
Example:
Table1:
Select * from Trans;
Loosen table Table1;
Note!
Should QlikView find circular references in the data structure which cannot be broken by tables declared loosely coupled interactively or explicitly in the script, one or more additional tables will be forced loosely coupled until no circular references remain. When this happens, the Loop Warning dialog, gives a warning.
, and more than once 
, and in the different ways 
. So, I'm not touching this feature anymore. Especially now, when QV has set analysis so we can ignore selections in a more reliable way.