You can install a plug-in by importing the plug-in's JAR file. When you import a plug-in, you lock down the provisioning system until the import is complete.
The following tasks also require a lock-down of the provisioning system. This means that you cannot begin importing a plug-in if one of these operations is being executed. You also cannot start one of these operations when you are importing a plug-in.
Saving a component type
Saving a system service
Moving or renaming a component
Moving or renaming a plan
Moving or renaming a folder
Deleting any object