Oracle Count Big table

How to count (*) big table in oracle ?

if 2 cpu then we can put no of parallel process 2 X 4  = 8 


select /*+ parallel (ttable, 8) */ count(*) from &table_name ttable ;



select /*+ parallel (ttable, 8) */ count(*) from anuj.user_site ttable ;



  COUNT(*)

----------

 280973975



Elapsed: 00:02:10.96

set linesize 200 time on timing on 
define table_name='XXX.XXX' ----- owner.table 
col human_readable for a15
select /*+ parallel (ttable, 50) opt_param('parallel_execution_enabled', 'true') */ count(*) count, dbms_xplan.format_number(count(*)) human_readable from &table_name ttable ;

cpu info 



col STAT_NAME 	for a30
col VALUE 	    for a15
SELECT STAT_NAME, TO_CHAR (VALUE) AS VALUE, COMMENTS   FROM v$osstat
WHERE stat_name IN ('NUM_CPUS', 'NUM_CPU_CORES', 'NUM_CPU_SOCKETS')
UNION
SELECT STAT_NAME, trunc(VALUE / 1024 / 1024 / 1024) || ' GB', COMMENTS   FROM v$osstat
WHERE stat_name IN ('PHYSICAL_MEMORY_BYTES');

====

col param_name 			format a40 heading 	"Parameter Name"
col param_value 		format a38 heading 	"Parameter Value" word_wrap
col isdefault 			format a7 heading 	"Default|Value"

col isses_modifiable 	format a10 heading 	"Session|Modifiable"
col issys_modifiable 	format a10 heading 	"System|Modifiable"
col ismod                          heading 	"Is|Modified"


set linesize 500
col DISPLAY_VALUE for a20 
col DEFAULT_VALUE for a20 
col VALUE for a20
col UPDATE_COMMENT for a20
col DESCRIPTION for a20 
col NAME for a35
 select *
 from v$parameter
 where name in ('cpu_count', 'parallel_threads_per_cpu', 'parallel_degree_policy', 'parallel_degree_limit');

                                                                                                                    Default Session    System
       NUM NAME                                      TYPE VALUE                DISPLAY_VALUE        DEFAULT_VALUE        Value   Modifiable Modifiable ISPDB ISINS ISMODIFIED ISADJ ISDEP ISBAS DESCRIPTION          UPDATE_COMMENT             HASH     CON_ID
---------- ----------------------------------- ---------- -------------------- -------------------- -------------------- ------- ---------- ---------- ----- ----- ---------- ----- ----- ----- -------------------- -------------------- ---------- ----------
       111 cpu_count                                    3 16                   16                   0                    TRUE    FALSE      IMMEDIATE  TRUE  TRUE  FALSE      FALSE FALSE FALSE number of CPUs for t                      1095434542          3
                                                                                                                                                                                                his instance

      3392 parallel_degree_policy                       2 AUTO                 AUTO                 MANUAL               FALSE   TRUE       IMMEDIATE  TRUE  TRUE  FALSE      FALSE FALSE FALSE policy used to compu                      1979359697          3
                                                                                                                                                                                                te the degree of par
                                                                                                                                                                                                allelism (MANUAL/LIM
                                                                                                                                                                                                ITED/AUTO/ADAPTIVE)

      3403 parallel_threads_per_cpu                     3 2                    2                    2                    TRUE    FALSE      IMMEDIATE  FALSE TRUE  FALSE      FALSE FALSE FALSE number of parallel e                      1020981983          3
                                                                                                                                                                                                xecution threads per
                                                                                                                                                                                                 CPU

      3776 parallel_degree_limit                        2 CPU                  CPU                  CPU                  TRUE    TRUE       IMMEDIATE  TRUE  TRUE  FALSE      FALSE FALSE FALSE limit placed on degr                      3004872640          3
                                                                                                                                                                                                ee of parallelism

===

Parallel_index Hint Is Not Honored (Doc ID 2294720.1)

he index is not partitioned.
So, you cannot use the parallel_index hint.