How do I Manage Access to Google Apps Services?
Depending on the size and type of organization you work in, enabling or disabling access to a variety of Google Apps services can be tedious and time consuming. You may want a certain group of users to have access to Google Chat or Google+, while disabling access to these services for other users.
Google makes enabling or disabling services for certain users simple through the use of organizational units. An org. unit, often confused with a Google Group, serves the main function of grouping users into a specific section in order to enable or disable services for those users. On the other hand, a Group acts as a forum and distribution list. A very important difference, for the purpose of turning services on and off, is that users may belong to multiple Groups while each user can only be placed in one org. unit.
The ability to restrict or enable access to Google Apps services and Marketplace extensions makes life easier for IT administrators. Customization based on the level of responsibility of an organizational unit allows administrators to delegate access to the appropriate people without having to enable or disable the service for each individual user. The org. unit structure also makes enabling or disabling services particularly simple when someone new joins your organization.