How about the UNDO tablespace, can i decrease the size ONLINE?

[Harry_Potter]

I have 2 datafiles in my UNDO tablespace, their sizes were 25GB each. I want it to trim down to 5GB each, can i do this ONLINE without shutting down the DB? if so, how can i do this?

[KenEwald]

Create a new undo tablespace, alter system set undo_tablespace *new tablespace* then drop the old one.

[davey23uk]

I have 2 datafiles in my UNDO tablespace, their sizes were 25GB each. I want it to trim down to 5GB each, can i do this ONLINE without shutting down the DB? if so, how can i do this?

yes, just resize the datafile downwards, and if it can resize it will