Terracotta has dev-console and ops-center monitoring utility which can show you lot of information about Terracotta cluster. You can find these utility in Terracotta_dir/bin folder.
The Terracotta server publishes a number of MBeans to provide information on the operation of the cluster.You can these MBeans via connecting Jconsole:
For example:
jconsole -J-Djava.class.path="<JDK installation dir>\lib\jconsole.jar;<JDK installation dir>\lib\tools.jar;<Terracotta installation Dir>\lib\jmxremote_optional-tc-1.0.1.jar;<Terracotta installation Dir>\lib\tc.jar" service:jmx:jmxmp://<Terracotta server IP>:9520