UKOUG Apps 18 Conference, Liverpool

Friday, March 02, 2018

Setting Oracle Session Parameters for Specific Process Scheduler Processes

This note describes a mechanism for setting initialisation parameters for specific processes run on the process scheduler. I will demonstrate it relation to nVision, but it has general application in PeopleSoft.
A table is used to hold metadata that described what setting is applied to which processes. A trigger on the process scheduler request table PSPRCSRQST reads that data and alters the session setting. This approach is easier to adjust and understand that static PL/SQL code in a trigger.
NB: The PSAESRV server process is used to run application engine programs in the process scheduler by default.  It should only be used for very short-lived programs and should usually be deconfigured. It maintains a persistent connection to the database. Therefore, session parameters set for one application engine program will carry forward into subsequent programs run on the same server process with the potential for unintended and unpredictable results. Other processes all establish their own database session that ends when the process terminates. This trigger mechanism can be still used to set parameters for some processes that run on PSAESRV, but the default parameter value should then be set for all other application engine processes. 

Metadata 

The table that holds the metadata should be defined in Application Designer.
CREATE TABLE PS_PRCS_SESS_PARM (PRCSTYPE VARCHAR2(30) NOT NULL,
   PRCSNAME VARCHAR2(12) NOT NULL,
   OPRID VARCHAR2(30) NOT NULL,
   RUNCNTLID VARCHAR2(30) NOT NULL,
   KEYWORD VARCHAR2(8) NOT NULL,
   PARAM_NAME VARCHAR2(50) NOT NULL,
   PARMVALUE VARCHAR2(128) NOT NULL) TABLESPACE PTTBL STORAGE (INITIAL
 40000 NEXT 100000 MAXEXTENTS UNLIMITED PCTINCREASE 0) PCTFREE 10
 PCTUSED 80
/
CREATE UNIQUE  iNDEX PS_PRCS_SESS_PARM ON PS_PRCS_SESS_PARM (PRCSTYPE,
   PRCSNAME,
   OPRID,
   RUNCNTLID,
   PARAM_NAME) TABLESPACE PSINDEX STORAGE (INITIAL 40000 NEXT 100000
 MAXEXTENTS UNLIMITED PCTINCREASE 0) PCTFREE 10 PARALLEL NOLOGGING
/
ALTER INDEX PS_PRCS_SESS_PARM NOPARALLEL LOGGING
/
I will demonstrate this mechanism for nVision. The metadata is simply inserted into the table by script.
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue)
VALUES ('nVision-ReportBook','RPTBOOK',' ',' ', 'SET', 'parallel_degree_policy','auto');
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue)
VALUES ('nVision-ReportBook','RPTBOOK',' ',' ', 'SET', 'parallel_degree_limit','4');
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue)
VALUES ('nVision-ReportBook','RPTBOOK',' ',' ', 'SET', 'parallel_degree_level','150');
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue)
VALUES ('nVision-ReportBook','RPTBOOK',' ',' ', 'SET', 'parallel_min_time_threshold','1');
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue)
VALUES ('nVision-ReportBook','RPTBOOK',' ',' ', 'SET', '_optimizer_skip_scan_enabled','FALSE');
Here we have 5 session parameters that will apply to all nVision reportbooks, but which I don't want to apply to the rest of the system.
PRCSTYPE             PRCSNAME     OPRID      RUNCNTLID                KEYWORD  PARAM_NAME                  PARMVALUE
-------------------- ------------ ---------- ------------------------ -------- ------------------------------ --------------------
nVision-ReportBook   RPTBOOK                                          SET      parallel_degree_policy         auto
nVision-ReportBook   RPTBOOK                                          SET      parallel_degree_limit          4
nVision-ReportBook   RPTBOOK                                          SET      _optimizer_skip_scan_enabled   FALSE
nVision-ReportBook   RPTBOOK                                          SET      parallel_min_time_threshold    1
nVision-ReportBook   RPTBOOK                                          SET      parallel_degree_level          150
The objective is to use limited parallelism only in the nVision reporting, and without decorating underlying ledger tables
  • parallel_degree_policy=auto enables the new 12c automatic degree of parallel calculation, statement queuing. 
  • parallel_min_time_threshold is set to 1 second. The default is 10. Statements whose runtime is estimated to be greater than or equal to this value will be considered for automatic degree of parallelism. 
  • parallel_degree_limit=4 restricts the automatic degree of parallelism to 4 to prevent any one statement using excessive parallelism.
  • parallel_degree_level=150 scales the automatic degree of parallelism calculation but within the parallel_degree_limit. This parameter is not officially documented, but See Kerry Osborne's blog 12c – parallel_degree_level (control for auto DOP).   
  • _optimiser_skip_scan_enabled=FALSE disables index skip scan to promote the use of smart full scan and Bloom filtering. It is recommended for engineered systems in Advice for the PeopleSoft DBA. Skip scan can prevent the optimizer choosing a smart full scan, so it makes sense to limits the setting to just nVision. I can also specify a parameter that will only be set when the reportbook is run by a particular operator with a particular run control.
The specific setting for one particular operation ID and run control takes precedence of the generic setting for all reportbooks.
INSERT INTO sysadm.PS_PRCS_SESS_PARM (prcstype, prcsname, oprid, runcntlid, keyword, param_name, parmvalue) 
VALUES ('nVision-ReportBook','RPTBOOK','NVOPR','NVSRBK_2', 'SET', 'parallel_degree_level','200');
In this case, I will scale the degree of parallelism further for a particular reportbook by setting parallel degree level to 20.
PRCSTYPE             PRCSNAME     OPRID      RUNCNTLID                KEYWORD  PARAM_NAME                  PARMVALUE
-------------------- ------------ ---------- ------------------------ -------- ------------------------------ --------------------
…
nVision-ReportBook   RPTBOOK                                          SET      parallel_degree_level          150
nVision-ReportBook   RPTBOOK      NVOPR      NVSRBK_2                 SET      parallel_degree_level          200

Trigger 

When a process starts the first thing it does is update its own status to 7 to indicate that it is processing. This is another example of a trigger created on that transition that injects behaviour at the start of a PeopleSoft process. This trigger reads the metadata and applies the settings with an ALTER SESSION command. The process type, name, operation and run control attributes must exactly match the process request, but a blank space is treated as a wildcard. Underscore parameters must be delimited in double quotes.
CREATE OR REPLACE TRIGGER sysadm.set_prcs_sess_parm
BEFORE UPDATE OF runstatus ON sysadm.psprcsrqst
FOR EACH ROW
WHEN (new.runstatus = 7 AND old.runstatus != 7 AND new.prcstype != 'PSJob')
DECLARE
  l_cmd VARCHAR2(100 CHAR);
  l_delim VARCHAR2(1 CHAR) := '';
  l_op VARCHAR2(1 CHAR) := '=';
BEGIN
  dbms_output.put_line('Row:'||:new.prcstype||'.'||:new.prcsname||':'||:new.oprid||'.'||:new.runcntlid);

  FOR i IN (
    WITH x as (
      SELECT p.*
      ,      row_number() over (partition by param_name 
                               order by NULLIF(prcstype, ' ') nulls last,
                                        NULLIF(prcsname, ' ') nulls last,
                                        NULLIF(oprid, ' ') nulls last,
                                        NULLIF(runcntlid,' ') nulls last
                              ) priority
      FROM   sysadm.PS_PRCS_SESS_PARM p
      WHERE  (p.prcstype  = :new.prcstype  OR p.prcstype  = ' ')
      AND    (p.prcsname  = :new.prcsname  OR p.prcsname  = ' ')
      AND    (p.oprid     = :new.oprid     OR p.oprid     = ' ')
      AND    (p.runcntlid = :new.runcntlid OR p.runcntlid = ' ')
    ) 
    SELECT * FROM x WHERE priority = 1 
  ) LOOP

    IF UPPER(i.keyword) = 'SET' THEN
      l_op := '=';
      IF SUBSTR(i.param_name,1,1) = '_' THEN 
        l_delim := '"';
      ELSE
        l_delim := '';
      END IF;   
    ELSE 
      l_op := ' ';
      l_delim := '';
    END IF;

    IF NULLIF(i.parmvalue,' ') IS NOT NULL THEN
      dbms_output.put_line('Rule:'||NVL(NULLIF(i.prcstype,' '),'*')
                             ||'.'||NVL(NULLIF(i.prcsname,' '),'*')
                             ||':'||NVL(NULLIF(i.oprid,' '),'*')
                             ||'.'||NVL(NULLIF(i.runcntlid,' '),'*')
                             ||':'||i.keyword||':'||i.param_name||l_op||i.parmvalue);

      l_cmd := 'ALTER SESSION '||i.keyword||' '||l_delim||i.param_name||l_delim||l_op||i.parmvalue;
      dbms_output.put_line('PI='||:new.prcsinstance||':'||:new.prcstype||'.'||:new.prcsname||':'
                                ||:new.oprid||'.'||:new.runcntlid||':'||l_cmd);
      EXECUTE IMMEDIATE l_cmd;
    END IF;
  END LOOP;
EXCEPTION
  WHEN OTHERS THEN
    dbms_output.put_line(sqlerrm);
END;
/
The trigger script set_prcs_sess_parm.sql can be download from my miscellaneous PeopleSoft scripts repository on Github.

Testing 

The trigger can be tested by updating the process scheduler request table in SQL*Plus, but be careful to roll back the update afterwards rather than committing. The trigger writes debug information to the server output that can be seen in SQL*Plus showing the rule being used and the ALTER SESSION command generated. However, this output is not captured in any PeopleSoft log when the trigger is fired by a PeopleSoft process.
set serveroutput on 
update psprcsrqst set runstatus = 7 where runstatus != 7
and prcsname = 'RPTBOOK' and runcntlid = 'NVSRBK_2' and oprid = 'NVOPR' and rownum = 1;
rollback;

Rule:nVision-ReportBook.RPTBOOK:*.*:_optimizer_skip_scan_enabled=FALSE
PI=3543986:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:ALTER SESSION SET "_optimizer_skip_scan_enabled"=FALSE
Rule:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:parallel_degree_level=200
PI=3543986:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:ALTER SESSION SET parallel_degree_level=200
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_degree_limit=4
PI=3543986:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:ALTER SESSION SET parallel_degree_limit=4
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_degree_policy=auto
PI=3543986:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:ALTER SESSION SET parallel_degree_policy=auto
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_min_time_threshold=1
PI=3543986:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_2:ALTER SESSION SET parallel_min_time_threshold=1
In the above example, the specific rule for NVSRBK_2 was applied setting PARALLEL_DEGREE_LEVEL to 200, whereas in the next example the generic setting of 150 is applied to NVSRBK_1.
update psprcsrqst set runstatus = 7 where runstatus != 7
and prcsname = 'RPTBOOK' and runcntlid = 'NVSRBK_1' and oprid = 'NVOPR' and rownum = 1;
rollback;

Rule:nVision-ReportBook.RPTBOOK:*.*:_optimizer_skip_scan_enabled=FALSE
PI=3543964:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_1:ALTER SESSION SET "_optimizer_skip_scan_enabled"=FALSE
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_degree_level=150
PI=3543964:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_1:ALTER SESSION SET parallel_degree_level=150
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_degree_limit=4
PI=3543964:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_1:ALTER SESSION SET parallel_degree_limit=4
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_degree_policy=auto
PI=3543964:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_1:ALTER SESSION SET parallel_degree_policy=auto
Rule:nVision-ReportBook.RPTBOOK:*.*:parallel_min_time_threshold=1
PI=3543964:nVision-ReportBook.RPTBOOK:NVOPR.NVSRBK_1:ALTER SESSION SET parallel_min_time_threshold=1

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