Why does my computer become unresponsive during the Volume Structures test?

Beginning in Techtool Pro 10, the volume structures of the startup volume can be tested without starting up from an alternate startup volume, such as an eDrive. In order to test the active startup volume, it must be "frozen" so that no changes are made to the volume during testing. Because the volume is frozen, the system typically becomes unresponsive until the test has completed and the drive is unfrozen. During this period, you may not be able to open other applications, and the Techtool Pro interface itself may become unresponsive as well. This is completely normal, and the system will become responsive again once the test has completed.