ORA-01450: maximum key length (3215) exceeded

SQL> alter index indx_cdr rebuild online;
alter index IDX_CDR rebuild online
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-01450: maximum key length (3215) exceeded



SQL> select max(length( call_message)) from  cdr;

MAX(LENGTH(CALL_MESSAGE))
-------------------------
               3586

SQL> alter index indx_cdr rebuild;

Index altered.