Oracle reorganize lob segement
Can I use the same tablespace the lob is in?


Yes.


  The total free space in that tablespace needs to be 200Gb?


No. Depends on the amount of data in your LOB segment. If your segment is 200 GB, but you have only 5 GB data in it (because the rest of the data was deleted), then you do not need 200 GB.


  During moving the lob is locked?


Not necessarily. Starting with 12.2, alter table has the move online option:

alter table mytable move online lob (lob_column) store as (tablespace users);


The above option is not available in 12.1.