If we are not giving Terracotta Server Array url while creating Add Cache Manager what difference it will make?

Hii All ,
I want to know what this url (Terracotta Server Array )
is used for?
please specify difference between giving url and not giving url?

Settings > Caching > Add Cache Manager.
aaa

The Terracotta Server Array is used by Integration Server to form a cluster. It allows multiple Integration Servers to share session state. See Using Terracotta with webMethods Products for more information about how IS uses the TSA.

Note that Integration Servers can also participate in a “stateless cluster.” This allows multiple ISes to work as a cluster but not share session state. There are some capabilities available to clusters that are not available to stateless clusters. Perhaps someone who knows where that is documented can post a link on this thread.

Please have a look @ Untitled (softwareag.com) and search for “Setting up the Terracotta Server Array for Use by the Cluster of Integration Servers”