pplied to all the devices. In some cases, it might be desirable only to execute the rollback for failed devices and to continue configuring other devices. For such options there are four types of rollback level: task level, device level, sub-task level and combined task level. In a task-level rollback, if a device cannot be configured, then rollback will be car- ried out for all previously configured devices, including the device for which config- uration failed, thus restoring the previous state. Configuration will not be attempted for the unconfigured devices. In a device-level rollback, if a device is not configured, then rollback will only be applied to that device and configuration of the other devices will continue. In the case of combined tasks, a task will contain many sub-tasks. When one sub- task fails, then rollback can be applied to devices in that sub-task only - and this is done using sub-task-level rollback. Suppose that there are three sub-tasks, S1, S2 and S3, in a combined task, and after S1 is successful a device fails in sub-task S2, then the combined task level rolls back all devices in S2 in addition to S1. Sub-task S3 will not be attempted for configuration. 11.2.8 Synchronizing the Inventory Database As in Chapter 10, we are again faced with the overlap between configuration man- agement and inventory management, at least at the "logical" level of inventory. CMS can be used to configure a set of devices with a particular task. Once these tasks executed over a set of devices, the information about the devices that have been con- figured will be stored. After configuring a device, it may be necessary to synchronise the inventory database so that it is updated with the new details. For example, when changing the "name" property of a device, it may be necessary to update the database with this information in order to change the device proper- ties to synchronise them with the new values. An interface has been provided for this purpose which can be used to update the managed object properties i