About real time statistics oracle 19c only for particular table
First up, you should only change underscore parameters when instructed to do so by support. But more importantly for these parameters, Real-Time Statistics is only available on specific database offerings. See the license guide for details.

Changing these parameters is likely to be a violation of your license agreement!


  LOAD TABLE CONVENTIONAL and OPTIMIZER STATISTICS GATHERING are the new
  parameters that have been added to the explain plan for this new
  feature.


These operations are not specific to Real-Time Statistics. OPTIMIZER STATISTICS GATHERING is for any operation that captures stats during execution. create table as select is an example that has done this for a while now.

LOAD TABLE CONVENTIONAL means the database does a conventional (not direct-path) insert.

You can disable Real-Time Statistics for:


A specific statement with the no_gather_optimizer_statistics hint
A table by locking stats for that table (though this will stop the background job gathering stats too!)


For example, only the first of these three inserts has the OPTIMIZER STATISTICS GATHERING operation:

set long 10000
set serveroutput off
cl scr
create table t as 
  select 1 c1 from dual
  connect by level &lt;= 100;

insert /*+ monitor */into t 
with rws as (
  select level x from dual
  connect by level &lt;= 10
)
  select * from rws;

select dbms_sqltune.report_sql_monitor (report_level=&gt; 'basic +plan')
from   dual;

SQL Plan Monitoring Details (Plan Hash Value=2403765415)
======================================================================================================================================================
| Id |             Operation             | Name |  Rows   | Cost |   Time    | Start  | Execs |   Rows   | Read | Read  | Activity | Activity Detail |
|    |                                   |      | (Estim) |      | Active(s) | Active |       | (Actual) | Reqs | Bytes |   (%)    |   (# samples)   |
======================================================================================================================================================
|  0 | INSERT STATEMENT                  |      |         |      |         1 |     +0 |     1 |        0 |      |       |          |                 |
|  1 |   LOAD TABLE CONVENTIONAL         | T    |         |      |         1 |     +0 |     1 |        0 |    4 | 32768 |          |                 |
|  2 |    OPTIMIZER STATISTICS GATHERING |      |       1 |    2 |         1 |     +0 |     1 |       10 |      |       |          |                 |
|  3 |     VIEW                          |      |       1 |    2 |         1 |     +0 |     1 |       10 |      |       |          |                 |
|  4 |      CONNECT BY WITHOUT FILTERING |      |         |      |         1 |     +0 |     1 |       10 |      |       |          |                 |
|  5 |       FAST DUAL                   |      |       1 |    2 |         1 |     +0 |     1 |        1 |      |       |          |                 |
======================================================================================================================================================    

insert /*+ monitor no_gather_optimizer_statistics */ into t 
with rws as (
  select level x from dual
  connect by level &lt;= 10
)
  select * from rws;

select dbms_sqltune.report_sql_monitor (report_level=&gt; 'basic +plan')
from   dual;

SQL Plan Monitoring Details (Plan Hash Value=2403765415)
======================================================================================================================================
| Id |            Operation             | Name |  Rows   | Cost |   Time    | Start  | Execs |   Rows   | Activity | Activity Detail |
|    |                                  |      | (Estim) |      | Active(s) | Active |       | (Actual) |   (%)    |   (# samples)   |
======================================================================================================================================
|  0 | INSERT STATEMENT                 |      |         |      |         1 |     +0 |     1 |        0 |          |                 |
|  1 |   LOAD TABLE CONVENTIONAL        | T    |         |      |         1 |     +0 |     1 |        0 |          |                 |
|  2 |    VIEW                          |      |       1 |    2 |         1 |     +0 |     1 |       10 |          |                 |
|  3 |     CONNECT BY WITHOUT FILTERING |      |         |      |         1 |     +0 |     1 |       10 |          |                 |
|  4 |      FAST DUAL                   |      |       1 |    2 |         1 |     +0 |     1 |        1 |          |                 |
======================================================================================================================================    

exec dbms_stats.lock_table_stats ( user, 'T' );

insert /*+ monitor */into t 
with rws as (
  select level x from dual
  connect by level &lt;= 10
)
  select * from rws;

select dbms_sqltune.report_sql_monitor (report_level=&gt; 'basic +plan')
from   dual;

SQL Plan Monitoring Details (Plan Hash Value=2403765415)
======================================================================================================================================
| Id |            Operation             | Name |  Rows   | Cost |   Time    | Start  | Execs |   Rows   | Activity | Activity Detail |
|    |                                  |      | (Estim) |      | Active(s) | Active |       | (Actual) |   (%)    |   (# samples)   |
======================================================================================================================================
|  0 | INSERT STATEMENT                 |      |         |      |         1 |     +0 |     1 |        0 |          |                 |
|  1 |   LOAD TABLE CONVENTIONAL        | T    |         |      |         1 |     +0 |     1 |        0 |          |                 |
|  2 |    VIEW                          |      |       1 |    2 |         1 |     +0 |     1 |       10 |          |                 |
|  3 |     CONNECT BY WITHOUT FILTERING |      |         |      |         1 |     +0 |     1 |       10 |          |                 |
|  4 |      FAST DUAL                   |      |       1 |    2 |         1 |     +0 |     1 |        1 |          |                 |
======================================================================================================================================  



  as we know getting real time statistics for any dml operation thats
  occuring for more that 100k rows is very costly operation


How do you know this?