Modifying media ID generation rule

If I modify the media ID generation rule for a robot, will it affect the existing media in the EMM database ? Actually I'm planning to create a media rule to use first 6 characters of of barcode. But there are already few media that for which media ID was generated using last 6 characters (default nature of netbackup).  If I change this rule all of sudden, will it impact previous media

Can I modify the media ID of a particular media with a new media in EMM ? say for example if the media ID is A00021 , can I modify it like 0021L3 ?