rebuild index 是，rebuild要紧跟索引名后面，在其他选项前面，否则会报错：
SQL> alter index IND_ABC rebuild;
Index altered.
SQL> alter index IND_ABC online rebuild;
alter index IND_ABC online rebuild
*
ERROR at line 1:
ORA-02243: invalid ALTER INDEX or ALTER MATERIALIZED VIEW option
online和rebuild调换位置：
SQL>
SQL> alter index IND_ABC rebuild online;
Index altered.