Assuming that if Lib B has these objects: X, Y, Z
and Lib A has these objects: U, V, W, X
and after the move Lib B should have: U, V, W, X, Y, Z
and Lib A should be empty
Then I would suspect that a save followed by a restore then a clrlib would
be your best bet. The restore should have an option to replace existing
objects. Keep in mind what ramifications there may be if 'U' is a LF
based off of 'V' if you evaluate other techniques.
And if Lib A is just a holding area for objects to be posted into B then
you have be sure that no one posts data while you are in progress. Concern
would be the object was inserted between the save and the clrlib.
Allocating the library exclusively during the run is one possible option.