So, I got this:
SQL> ALTER INDEX MATHEUS.INDEX_1 REBUILD online TABLESPACE NEW_TBS; ALTER INDEX MATHEUS.INDEX_1 REBUILD online TABLESPACE NEW_TBS * ERROR at line 1: ORA-00604: error occurred at recursive SQL level 1 ORA-01450: maximum key length (3215) exceeded
So, is this a bug? Yes it is.
From MOS ALTER INDEX REBUILD ONLINE Fails with ORA-01450 (Doc ID 236329.1):
“This is caused by issue Bug:2525767. The online rebuild of the index creates a journal table and index. This internal journal IOT table contains more columns in its index. Their total length is greater than number reported in ORA-01450 error message. This is a feature of online rebuild.
Maximum key length is calculated with respect to the database block size. It means that current value of the initialization parameter db_block_size is not large enough so that the internal journal IOT can be created without errors.”
Wanna know more, there is a great article on how this works exactly, by Alex Gorbachev: ORA-01450 During Online Index Rebuild
It simply cannot be done online as explained, so doing it offline is the solution:
SQL> ALTER INDEX MATHEUS.INDEX_1 REBUILD TABLESPACE NEW_TBS; Index altered.
Hope it helps, cheers!