In computer science, shadow paging is a technique for providing atomicity and durability (two of the ACID properties) in database systems.
A page in this context refers to a unit of physical storage (probably on a hard disk), typically of the order of 1 to 64 KiB.
[citation needed] Shadow paging is similar to the old master–new master batch processing technique used in mainframe database systems.
In these systems, the output of each batch run (possibly a day's work) was written to two separate disks or other form of storage medium.
Shadow paging is also similar to purely functional data structures, in that in-place updates are avoided.