Cisco Configuration Replace and Configuration Rollback

Beginning in Cisco IOS Software Release 12.3(7)T, the Configuration Replace and Configuration Rollback features allow for archiving of the Cisco IOS device configuration on the device. Stored manually or automatically, the configurations in this archive can be used in order to replace the current running configuration using the configure replace filename command.

This is in contrast to the copy filename running-config command. The configure replace filename command replaces the running configuration as opposed to the merge performed by the copy command.
You are advised to enable this feature on all Cisco IOS devices in the network.

Once enabled, an administrator can cause the current running configuration to be added to the archive by using the archive config privileged EXEC command. The archived configurations can be viewed using the show archive EXEC command.
This example illustrates the configuration of automatic configuration archiving. This example instructs the Cisco IOS device to store archived configurations as files named archived-config-N on the disk0: file system, to maintain a maximum of 14 backups, and to archive once per day (1440 minutes) and when an administrator issues the write memory EXEC command.
!
archive
path disk0:archived-config
maximum 14
time-period 1440
write-memory
!
Although the configuration archive functionality can store up to 14 backup configurations, you are advised to consider the space requirements before using the maximum command.

Reference : http://www.cisco.com/en/US/docs/ios/12_3t/12_3t7/feature/guide/gtrollbk.html