Decommissioning is the process of shutting down and disassembling a system or facility for various reasons like outdatedness, maintenance, or security concerns. The antonyms for decommission include phrases like commissioning or activation. Commissioning refers to the process of setting up a system, equipment, or facility for operation or use. On the other hand, activation involves making something active or operational, bringing it back into use after a period of inactivity or shutdown. The antonyms of decommission also include phrases such as construction, installation, establishment, and initiation, which refer to the processes of building, installing, starting, or setting up a system, asset, or facility for use.