Figure 1-1 Storage savings with ProtecTIER HyperFactor The effect and result of HyperFactor processing is a  factoring ratio . In simple words, the  factoring ratio is the ratio of nominal data (as a sum of all user data backed up) to the  occupied physical storage in ProtecTIER repository. Two key elements affect your factoring ratio and the effectiveness of your ProtecTIER  environments: Data retention period The period, which is measured in days, for which the backup  application keeps the data available in its disk or tape repository.  Typical retention periods of user data and applications are not  longer than 90 days. Typical retention periods for database  backups are not longer than 30 days, but specific weekly or  monthly snapshots can be stored for months or even years. Tip:  A longer retention period increases the factoring ratio of  your ProtecTIER product. Data change rate The average percentage of data that is received from the backup  application that changed from the previous backup iteration. This  parameter is important when you size the backup repository and  planning for optimal backup windows of various applications or  systems.  Examples of typical applications to be sized are progressive forever  incremental backups and online database backups (IBM Lotusfi,  IBM Dominofi, Oracle, SAP, IBM DB2fi, Microsoft SQL, MaxDB,  and so on). The data change rate might vary from platform to  platform (from 1% to greater than 25%). Tip:  Less changing of data improves the deduplication process  and boosts the factoring ratio. 10  IBM ProtecTIER Implementation and Best Practices Guide