Oracle Database Discussions

Max_parallel_servers can be different on each of your instances. The DOP=6 looks to real Be Reporting That you’re using 6 instances.

The majority of the time taken in this execution doesn’t seem to have anything to do with the amount of parallelism, it looks to be mostly due to the “TABLE ACCESS STORAGE FULL FIRST ROWS“ which seems to be executed 12 million times on line 18. This looks to be a result of your statement written using scalar subqueries with rownum filters in them - forcing a row-by-row (slow by slow!) type of plan that doesn’t take advantage of bulky techniques that would fly through this work in parallel.

If you share your SQL, I’m sure we can suggest a much better way to write it.

Hi Andrew -Thank you for the help -

Version is 12.1 and below is the SQL TEXT -

UPDATE pgn_scrpt_tmp_tbl scrpt_tbl
SET
    scrpt_tbl.rx_nbr = NULL,
    scrpt_tbl.days_supply_qty = 0
WHERE
scrpt_tbl.rowid IN (
    SELECT
        ROWID row_id
    FROM
        pgn_scrpt_tmp_tbl
    WHERE
            pgn_clas IS NULL
        AND (
                EXISTS (
                    SELECT
                        1
                    FROM
                        pci_vw.rule_config_file_parm config
                    WHERE
                            config.config_file_id = 101
                        AND
                            config.config_parm1_id = 1001
                        AND
                            config.config_parm1_val = rxc_pat_id
                        AND
                            config.curr_ind = 'Y'
                )
            OR
                EXISTS (
                    SELECT
                        1
                    FROM
                        pci_vw.rule_config_file_parm config
                    WHERE
                            config.config_file_id = 104
                        AND
                            config.config_parm1_id = 1003
                        AND
                            config.config_parm1_val = store_nbr
                        AND
                            config.curr_ind = 'Y'
                )
            OR
                dea BETWEEN 2 AND 5
            OR
                trunc(months_between(
                    TO_DATE('06012019','MMDDYYYY'),
                    trunc(birth_dt)
                ) / 12) <= 18
            OR
                trunc(months_between(
                    TO_DATE('06012019','MMDDYYYY'),
                    trunc(birth_dt)
                ) / 12) >= 120
        )
)

Thanks

Bhavani

hi Jonathon --Thank you for helping me with this request -

The Version is 12.1 and I just updated the SQL_TEXT as well -

we want to find the Actual slaves allocated for all the application query's  and I was basically using the SQL Monitor report Allocated Slaves section to find it  -

The Reason why we want to find Actual slaves:

we are Planning to use the DBRM to limit the DOP for the application and also want to Limit the Application only to 3 nodes where as the same application is using 8 nodes currently -That means the parallel query's are also limited to only 3 nodes despite the setting of parallel_force_local to TRUE Value  

The parallel_max_server value is 204 currently and application currently can use 8*204 parallel slaves if it wants -but after the DBRM since we are limiting to only 3 nodes ,it can only use 3*204 slaves --

So we want to see current utilization of parallel slaves and see if we can increase the value of parallel_max_servers  if required -

Question:

Is SQL Monitor report is reliable way of Finding the Slaves allocated?

is there any other best method to do this?

Thanks

Bhavani

Question:
 Is SQL Monitor report is reliable way of Finding the Slaves allocated?

Clearly it is not reliable since you've said your maximum possible number of PX processes is 8 * 204 and the report says that is has allocated 290,084 which is rather larger than the limit.  On the other hand I have explained that the report can count the number of processes once for every execution of the subquery, so that would explain the extreme excess, and it would be something that you want to investigate and modify the code to avoid since allocation and de-allocation of the same small set of slaves MIGHT REALLY be happening and increasing the workload dramatically.

is there any other best method to do this [find number of slaves allocated] ?

I suspect there is no method that will guarantee to give the right answer in all cases - every query with multiple DFO trees probably needs to be examined individually and watched while it is running if you want to find the maximum number of parallel servers sets (and slaves) it ever has allocated. There is the report_sql_monitor output which has a few holes, there is the v$pq_tqstat view (after you run a query) which has a few holes - both improve with version; and every time you upgrade you find that Oracle has enhanced parallel query processing to reduce resouse wastage.  (You don't say whether your version of Oracle is 12.1.0.1 or 12.1.0.2 - but the plan suggests it might be 12.1.0.1 - and in 12.2.0.1 you might find that Oracle either does some clever tricks with sub query unnesting or uses "single server  parallel access" or "expression evaluation" to eliminate the 2nd and 3rd DFO tress entirely).

Possibly counting the number of p0xx lines in the Parallel Execution Details section would be accurate enough - though I think in 11.2.0.4 I managed to get a report with thousands of lines (matched the value of Servers Allocated.

Regards

Jonathan Lewis

Bhavani Dhulipalla wrote:
Hi Andrew -Thank you for the help -
Version is 12.1 and below is the SQL TEXT -

UPDATE pgn_scrpt_tmp_tbl scrpt_tbl SET  scrpt_tbl.rx_nbr = NULL,  scrpt_tbl.days_supply_qty = 0 WHERE scrpt_tbl.rowid IN (  SELECT  ROWID row_id  FROM  pgn_scrpt_tmp_tbl  WHERE  pgn_clas IS NULL  AND (  EXISTS (  SELECT  1  FROM  pci_vw.rule_config_file_parm config  WHERE  config.config_file_id = 101  AND  config.config_parm1_id = 1001  AND  config.config_parm1_val = rxc_pat_id  AND  config.curr_ind = 'Y'  )  OR  EXISTS (  SELECT  1  FROM  pci_vw.rule_config_file_parm config  WHERE  config.config_file_id = 104  AND  config.config_parm1_id = 1003  AND  config.config_parm1_val = store_nbr  AND  config.curr_ind = 'Y'  )  OR  dea BETWEEN 2 AND 5  OR  trunc(months_between(  TO_DATE('06012019','MMDDYYYY'),  trunc(birth_dt)  ) / 12) <= 18  OR  trunc(months_between(  TO_DATE('06012019','MMDDYYYY'),  trunc(birth_dt)  ) / 12) >= 120  ) )

Thanks
Bhavani

You would probably get away with running this with much fewer DOP if you rewrote those ORs. Either you could do something like 3 separate deletes:

UPDATE pgn_scrpt_tmp_tbl scrpt_tbl

SET

    scrpt_tbl.rx_nbr = NULL,

    scrpt_tbl.days_supply_qty = 0

WHERE  pgn_clas IS NULL

AND    EXISTS (  SELECT

                     1

                 FROM

                     pci_vw.rule_config_file_parm config

                 WHERE

                         config.config_file_id = 101

                     AND

                         config.config_parm1_id = 1001

                     AND

                         config.config_parm1_val = rxc_pat_id

                     AND

                         config.curr_ind = 'Y'

             )

UPDATE pgn_scrpt_tmp_tbl scrpt_tbl

SET

    scrpt_tbl.rx_nbr = NULL,

    scrpt_tbl.days_supply_qty = 0

WHERE  pgn_clas IS NULL

AND    EXISTS (

               SELECT

                   1

               FROM

                   pci_vw.rule_config_file_parm config

               WHERE

                       config.config_file_id = 104

                   AND

                       config.config_parm1_id = 1003

                   AND

                       config.config_parm1_val = store_nbr

                   AND

                       config.curr_ind = 'Y'

           )

UPDATE pgn_scrpt_tmp_tbl scrpt_tbl

SET

    scrpt_tbl.rx_nbr = NULL,

    scrpt_tbl.days_supply_qty = 0

WHERE  pgn_clas IS NULL

AND    (

           dea BETWEEN 2 AND 5

       OR

           trunc(months_between(

               TO_DATE('06012019','MMDDYYYY'),

               trunc(birth_dt)

           ) / 12) <= 18

       OR

           trunc(months_between(

               TO_DATE('06012019','MMDDYYYY'),

               trunc(birth_dt)

           ) / 12) >= 120

)

Or you could try to use union all in the exists filters. Those changes should allow a hash join to be used for the existance check rather than having to execute them once per row (which just won't scale).