After you release the unused space, it becomes marked as  Pending  in the ProtecTIER  repository. The ProtecTIER repository then automatically uses internal processes to optimize  the available space for future backups: In the Capacity section of the ProtecTIER GUI (Figure 2-3), the pie chart at the right side  shows the nominal data, and you can see the pending space. In this example, the pending  space is 16.9 terabytes (TB). As a result of the delete operation, some fragmented space can occur, as shown in the pie  chart on the left in Figure 2-3. Further ProtecTIER internal housekeeping eliminates that  space. The newly reworked repository is perfectly aligned to your next incoming backup. From a technical standpoint, there is no problem with having a ProtecTIER repository that is  100% used (although from a usability standpoint it is not a good practice to permit a  repository to get 100% full). After you reach a steady state where daily housekeeping frees up  enough space to enable daily backups, a high usage is possible.  In reality, data tends to grow, so sooner or later you can face changed requirements for your  ProtecTIER repository size. You should configure an automated message that informs you  when the repository usage crosses a specified threshold value. Depending on the time you  need to prepare a capacity upgrade of the ProtecTIER back-end storage, values greater than  80% or 90% can be selected to provide ample time for preparation.  2.5.6 ProtecTIER repository usage GLYPH<SM590000> Internal Deleter processes reduce the Pending space and, in the process, create  Fragmented space.  GLYPH<SM590000> Internal Defragger processes then reduce the Fragmented space.  Figure 2-3 ProtecTIER repository with pending nominal space Chapter 2. Deduplication considerations  31