Procedure
•Open Model in CATIA Assembly Design.
•In the Assembly Feature toolbar select the Symmetry icon (insert icon).
•Choose the plane of symmetry.
•Select the assembly to be mirrored from the tree.
•Use the Symmetry Wizard to complete the operation.
•Change workbench to the current 3DCS Analysis package. A warning message will appear on the screen:
•Click the 3DCS drop-down list and select Data 
Mirror.
•Determine the naming convention with the prefix/suffix editor boxes.
•Select Duplicate button if the new assembly/part is a symmetry of the original assembly/part.
•Select Mirror button if the new assembly/part is a copy of the original assembly/part.
•Choose the Source object (part from the tree with original DCS data).
•Select the Target object (new duplicated part from the tree) which the data is to be mirrored onto.
•Click Apply to create the mirror part/assembly and exit the menu.