In many cases a backup should only be performed in certain machine states, e.g. when the machine is in home position. This ensures that all backed up data is consistent with each other and that the machine is immediately ready for use in case of a recovery.
In simple environments where there are clearly defined machine downtimes, the backup can also be time-controlled. This can be at night, for example, when production is at a standstill. However, there are more and more machines and plants that do not have longer downtimes. For these machines a PLC-controlled data backup is very important. This is the only way to ensure that the backup is stored consistently.