Figure 9-37 shows creating a cache partition. Figure 9-38 shows an example of successful creation in the upper half. The lower half shows  an example where the user failed to observe the amount of free space available in CP0. Notice that redefining the size of existing partitions in an operational TS7720T might create  unexpected load peak in the overall premigration queue, which causes host write throttling to  be applied to the partitions.  For example, consider the following example, where a tape attached partition is downsized,  and become instantly overcommitted. In this example, the TS7720T premigration queue is  flooded by volumes that got dislodged by the size of this cache partition becoming smaller.  Partition readapts to the new size by migrating volumes in excess to physical tape.  396  IBM TS7700 Release 4.2 Guide Figure 9-38 Example of a success and a failure to create a new partition Figure 9-37 Creating a cache partition