Scheduling Jobs in the Database

The PM_MEDIATION_TB table has the following structure.

Name	Null?	Type
APPLICATION_NAME	NOT NULL	VARCHAR2(30)
SERVICE_NAME	NOT NULL	VARCHAR2(30)
OPERATION_NAME	NOT NULL	VARCHAR2(50)
START_TIME	NOT NULL	TIMESTAMP(6)
END_TIME	NOT NULL	TIMESTAMP(6)
TOT_REQ	NUMBER
SUCCESS_COUNT	NUMBER
FAILURE_COUNT	NUMBER
AVAILABILITY	NUMBER

The above task is independent of other on-line systems and happens exclusively within the database. This task can be scheduled as a database job. The database job has its own control table to take care of failures for rerun independent of the scheduler table managed by Oracle. This control table contains the data window that is independent of the run window.

The function is required to run only on a timed cycle or at a denoted time. The DB job is akin to a batch process that is data-centric and can crunch efficiently through large volumes offline without affecting the on-line systems such as the access gateway.

The DB Job uses the following control table to maintain the timestamp. The DB job should start from specific time. This timestamp will be maintained in the Prev_timestamp column. When the DB job is started for the first time, the control table will be empty. When the job runs for the first time, you should get the min (start_time) from the PERFORMANCE_METRICS_TB as the prev_timestamp for the DB job to run.

CONTROL_TB

The control table is given as below

PROCESS_ID	PROCESS_NAME	PREV_TIMESTAMP
1	pr_AggregateMetrics	2007-9-18.14.25. 30. 149000000

When the procedure "pr_AggregateMetrics" runs for the first time, it takes the prev_timestamp = min(start_time) from PERFORMANCE_METRICS_TB.

You also can configure the data collection interval and repeat interval in the table PM_DELTA_CONFIG. Assume that the application populates these data during startup.

PM_DELTA_CONFIG

PROCESS_NAME	DATA_COLLECTION_ INTERVAL	REPEAT_INTERVAL
pr_AggregateMetrics	60 (in secs)	60 (in secs)

The database job will take prev_timestamp from the CONTROL_TB table. The end time is prev_timestamp + DATA_COLLECTION_INTERVAL. Once the job is successfully executed, it will update prev_timestamp with the end_time. The DB job calculates the no_of_chunks of data to be processed as

No_of_chunks = REPEAT_INTERVAL / DATA_COLLECTION_INTERVAL

The db job processes the "n" minute data when it wakes up every time. This "n" minute is configured as "data_collection_interval" in the table PM_DELTA_CONFIG.

The following is the PL/SQL procedure that aggregates the data from Performance_Metrics_TB and populates the aggregated data into PM_MEDIATION_TB.

PROMPT Creating Package Specification For pkg_PerformanceMetrics

CREATE OR REPLACE PACKAGE pkg_PerformanceMetrics AS

   -- Declaring the User Defined Exceptions in the Package Level.

   PM_Data_Not_Available_Excp EXCEPTION;
   PRAGMA EXCEPTION_INIT(PM_Data_Not_Available_Excp,-20100);

   Large_Data_Window_Excp EXCEPTION;
   PRAGMA EXCEPTION_INIT(Large_Data_Window_Excp,-20101);

  -- procedure declaration
   procedure pr_AggregateMetrics;

END pkg_PerformanceMetrics;
/

PROMPT Creating Package Body For pkg_PerformanceMetrics

CREATE or REPLACE package body pkg_PerformanceMetrics IS

PROCEDURE pr_AggregateMetrics AS

-- Declaring and Initializing the Variables
V_Err_Msg varchar2(4000);
V_Err_Code varchar2(100);
V_Err_Date  DATE:=sysdate;
V_Proc_Name varchar2(50):= 'pr_AggregateMetrics';

v_currenttime timestamp ;
v_prevtimestamp timestamp ;

v_datacollection_interval number;
v_repeat_interval number;
v_noofchunks number;

v_start_time timestamp;

v_commit_cnt number := 0;

v_Metrics_found boolean := false;

v_min_time timestamp;

v_reccount number;

-- Defining the Cursor with parameters previous time and current
-- time

cursor PM_MetricsInfo_cur(v_prevtimestamp IN timestamp,
                          v_currenttime IN timestamp) is
select  application_name,service_name,
        operation_name,start_time,end_time,
        sum(total_request) as total_request,
        sum(success_count)as success_count,
        sum(err_count) as failure_count ,
(sum(err_count)+sum(success_count))/sum(total_request) as
   availability
from PERFORMANCE_METRICS_TB
where start_time>=to_timestamp(to_char(v_prevtimestamp,
   'dd-mm-yyyy hh24:mi.ss.'),'dd-mm-yyyy hh24:mi.ss.') and
   to_timestamp(to_char(end_time,'dd-mm-yyyy hh24:mi.ss.'),
   'dd-mm-yyyy hh24:mi.ss.')<=v_currenttime
group by application_name,service_name,operation_name,
  start_time,end_time;

BEGIN
-- Getting the data_collection_interval,repeat interval from
-- PM_DELTA_CONFIG

   BEGIN
      select DATA_COLLECTION_INTERVAL,
             REPEAT_INTERVAL into v_datacollection_interval,
             v_repeat_interval
      from PM_DELTA_CONFIG where PROCESS_NAME='pr_AggregateMetrics';

   EXCEPTION
      WHEN NO_DATA_FOUND THEN
         DBMS_OUTPUT.PUT_LINE(V_Err_Date ||'—'||
            V_Proc_Name ||'—'|| 'Configuration details are missing
            in PM_DELTA_CONFIG');
         raise;
      WHEN TOO_MANY_ROWS THEN
         DBMS_OUTPUT.PUT_LINE(V_Err_Date ||'—'||
            V_Proc_Name ||'—'|| 'Exact fetch returns more than one
            row. Please check PM_DELTA_CONFIG tables');
         raise;
   END;

   IF (v_datacollection_interval>v_repeat_interval) THEN
      V_Err_Msg:='Data Window is larger than the repeat interval';

      --DBMS_OUTPUT.PUT_LINE(sysdate ||'—'|| V_Proc_Name ||'—'||
                             V_Err_Msg);
      raise_application_error(-20101, 'Data Window is larger than
                              the repeat interval');
   END IF;
   -- Finding out the number of chunks of data

   v_noofchunks := v_repeat_interval/v_datacollection_interval;

   For i in 1..v_noofchunks Loop
Begin

      Begin

   -- Get the previous timestamp from the control table for this
   -- procedure "pr_AggregateMetrics"

   select prev_timestamp into v_prevtimestamp
   from CONTROL_TB
   where process_name ='pr_AggregateMetrics';

Exception

   WHEN TOO_MANY_ROWS THEN
   V_Err_Msg:='Exact fetch returns more than one row.. Check the
      CONTROL_TB for PROCESS_NAME= pr_AggregateMetrics1';
   --DBMS_OUTPUT.PUT_LINE(sysdate ||'—'|| V_Proc_Name ||'—'||
                          V_Err_Msg);
   raise;

   WHEN NO_DATA_FOUND THEN
   BEGIN
      -- No data found in control table.
      -- Getting the min(start_time) from PERFORMANCE_METRICS_TB
      -- for the first run.

      select min(start_time) into v_start_time
      from PERFORMANCE_METRICS_TB;

      -- Updating the Control table with the start time.

      IF (v_start_time is not null) THEN
         insert into CONTROL_TB(process_ID,process_name,
                                prev_timestamp)
         values(1,'pr_AggregateMetrics1',v_start_time);
         commit;
         v_prevtimestamp := v_start_time;
      END IF;

   EXCEPTION
      WHEN NO_DATA_FOUND THEN
      V_Err_Msg:='Performance Metrics data is not yet populated';
      raise_application_error(-20100,'Performance Metrics data is
                              not yet populated');
   END;

End;

v_currenttime:= to_timestamp(to_char(v_prevtimestamp +
   v_datacollection_interval*(1/24/60/60),
   'dd-mm-yyyy hh24:mi:ss.')||to_char(to_number
   (to_char(v_prevtimestamp,'FF'))+250),
   'dd-mm-yyyy hh24:mi:ss.FF');


FOR Metric_rec in PM_MetricsInfo_cur(v_prevtimestamp,v_currenttime)
LOOP
   BEGIN
      -- DBMS_OUTPUT.PUT_LINE(sysdate ||'—'|| V_Proc_Name ||'—'||'
      -- Processing record with service name ' ||
      -- Metric_rec.service_name);

      v_Metrics_found := true;

      SELECT count(*) into v_reccount FROM PM_MEDIATION_TB
      WHERE service_name=Metric_rec.service_name and
      application_name= Metric_rec.application_name and
      operation_name = Metric_rec.operation_name and
      start_time=Metric_rec.start_time and
      end_time=Metric_rec.end_time;

      IF (v_reccount=0) THEN

         insert into PM_MEDIATION_TB (service_name,
            application_name, operation_name, start_time,
            end_time, tot_req, success_count,failure_count,
            availability)
         values(Metric_rec.service_name,
                Metric_rec.application_name,
                Metric_rec.operation_name,
                Metric_rec.start_time,
                Metric_rec.end_time,
                Metric_rec.total_request,
                Metric_rec.success_count,
                Metric_rec.failure_count,
                Metric_rec.availability
               );

      ELSE

         UPDATE PM_MEDIATION_TB
         SET tot_req=Metric_rec.total_request,
         success_count=Metric_rec.success_count,
         failure_count=Metric_rec.failure_count,
         availability=Metric_rec.availability
         WHERE service_name=Metric_rec.service_name and
         application_name= Metric_rec.application_name and
         operation_name = Metric_rec.operation_name and
         start_time=Metric_rec.start_time and
         end_time=Metric_rec.end_time;

      END IF;

   END;
   END LOOP;

      -- If the metrics are collected successfully,
      -- update the prevtimestamp into the CONTROL_TB

      IF (v_Metrics_found) THEN

         UPDATE CONTROL_TB
         SET prev_timestamp=v_currenttime
         WHERE PROCESS_NAME='pr_AggregateMetrics';
      END IF;

      -- Making the DB changes permanent
      COMMIT;

      IF (not v_Metrics_found) THEN

         select min(start_time) into v_min_time
         from PERFORMANCE_METRICS_TB
         where start_time>v_prevtimestamp;

         -- dbms_output.put_line('start_time : ' ||v_min_time
         -- || ' v_prevtimestamp : '||v_prevtimestamp);
         IF (v_min_time is not null) THEN
            UPDATE CONTROL_TB
            SET prev_timestamp=v_min_time
            WHERE PROCESS_NAME='pr_AggregateMetrics';
            COMMIT;
         END IF;
      END IF;
   END;
      v_Metrics_found := false;

   End Loop; -- for i loop

   EXCEPTION

      WHEN TOO_MANY_ROWS THEN
         V_Err_Msg :=SQLERRM;
         V_Err_Date:=sysdate;
      --DBMS_OUTPUT.PUT_LINE (sysdate ||'—'|| V_Proc_Name ||'—'||
      --V_Err_Msg);
      WHEN NO_DATA_FOUND THEN
         V_Err_Msg :=SQLERRM;
         V_Err_Date:=sysdate;
         ROLLBACK;
      --DBMS_OUTPUT.PUT_LINE (sysdate ||'—'|| V_Proc_Name ||'—'||
      --V_Err_Msg);


   WHEN PM_Data_Not_Available_Excp THEN
      V_Err_Msg :='Performance Data is not available';
      V_Err_Date:=sysdate;
      --DBMS_OUTPUT.PUT_LINE (sysdate ||'—'|| V_Proc_Name
      --||'—'|| V_Err_Msg);

      WHEN Large_Data_Window_Excp THEN
         V_Err_Msg:='';

      WHEN OTHERS THEN
         V_Err_Msg :=SQLERRM;
         ROLLBACK;
      --DBMS_OUTPUT.PUT_LINE (sysdate ||'—'|| V_Proc_Name
      --||'—'||V_Err_Msg);

END pr_AggregateMetrics;

END pkg_PerformanceMetrics;
/

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This article was originally published on November 30, 2007