The registry cache is held by the Registry Agent on each host, and it contains a list of the packages deployed on each host in your Framework. This list is a copy of part of the information held by the Registry Manager, and it enables Framework components to locate and communicate with each other, according to their position in the hierarchy created when you add domains and hosts to your Framework. Agents send requests to managers in the immediate subdomain, and if a request is unsuccessful, they try a manager higher up in the hierarchy.
You can view the registry cache to check hosts in your Framework to see if a specific manager or agent module is installed, and check the order in the Framework hierarchy according to the hosts the modules are installed on. See Viewing the Registry Cache.
If the registry cache becomes out-of-date, communication problems can occur. To fix this, try clearing the registry cache on the Registry Agent to allow it to be updated by the Registry Manager. See Clearing the Registry Cache.