The Checkout/Checkin Facility provides a level of source control that extends beyond the normal convention of allowing only one user to update a source file at any time.
A source file designated as under Checkout control cannot be edited directly. Rather, the source file is "checked out" by creating a copy of the file in another directory, typically a user's work directory. The original file is marked as being checked out and by whom. Other users are prevented from checking out this file until it has been "checked in". The newly created copy can be edited only by the user to whom the file had been checked out (although the file can be reassigned -- see the FileCheckAssign command). After the source file has been updated and tested, it is checked in.
Security can be defined which restricts access to the Checkout and Checkin operations. Typically, the Checkin operation for a particular directory is reserved for an administrative person.
The following commands comprise the Checkout/Checkin Facility: