1) umount needs to restore the element's vob (original vob), remove the tag and unregister it;
2) recover vob from the latest backup. Do not restore it to the original location. You can restore it to another temporary directory on the vob host (which can be created in advance ).
3) register the object for the recovered vob and create a tag named vob_a;
4) create a temporary vob_ B for storing restored elements and use it for intermediate storage;
5) use the cleartool relocate command to migrate the elements to be restored on vob_a to vob_ B;
6) Verify that the migrated elements are available and use the rmvob command to delete vob_a;
7) re-register the original vob and create a tag, and then mount the vob;
8) use the relocate command again to migrate the elements on vob_ B to the original vob;
9) Verify the required elements in the original vob;
10) run the rmvob command to delete the temporary vob_ B.