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Synchronization Points

A data synchronization point is a point in time. It is used to assess the way in which data backups relate to each other. Data backups need to be related to each other correctly when considering the time of day they were made, or their relationship to computer system activity events. A data synchronization point is a point in time when a set of backups exist which if restored from can be synchronized to the same point in time. Often this point in time is some hours before the last backup is completed, i.e., some hours before the data synchronization point. Backups that have no synchronization points are generally useless.

A frequent mistake when setting RPO for traditional daily tape offsited backups is to assume 24 hours for the RPO. This mistake is the result of not considering that the RPO time begins with the start of the first data backup used in the synchronization point; and must also include time for boxing the tapes; the inevitable contingency time that must be allowed for "waiting for courier transport"; loading and final escape from site (not always at exactly the same time of day – the RPO must be increased by an amount of time equivalent to any such variability). It is also risky to assume that tapes will always be physically intact – the RPO should include enough time to use a previous synchronization point, too.

Source: Wikipedia, Google