Protocol For Simultaneous Commit Within A Data Base With Multiple Independent Recoverable Segments
Original Publication Date: 1979-Oct-01
Included in the Prior Art Database: 2005-Feb-20
A data base system must supply a means to treat multiple changes to the data as one atomic change. An effective mechanism is to make all the changes not to the original data base, but to a copy of the data base. If something goes wrong during the data base modification, the copy can be ignored, and the data base remains unchanged. If all the modifications are successfully made, then the modified version of the data base becomes the actual data base, and the original unchanged portion is ignored. The switch from the old data base version to the new version must occur in one machine operation. A technique for accomplishing the above is to create shadow pages for the modified parts of the data base, and to switch the data base page tables from the original to the shadow pages when the changes are to be committed.