Let's look at what we can do with the Move Job API.
Earlier this month, over on Midrange-L, Becky B. wrote in with this:
During month-end we have a large number of user-submitted jobs that automatically go to the QBATCH job queue and hold up other jobs. Is there a way to automatically redirect jobs to a different subsystem once they hit the job queue?
Included was a follow-on note explaining that management was hoping for a silver bullet so that they wouldn't have to change the programs submitting month-end jobs.
One response, from Roger H., was this:
There is a job notification exit point that may be helpful to you QIBM_QWT_JOBNOTIFY. Here's an article by (who else?) Bruce Vining on using it http://www.mcpressonline.com/apis/the-api-corner-monitoring-a-job-queue.html
This month, we'll look at how the QIBM_QWT_JOBNOTIFY exit point, in conjunction with the Move Job (QSPMOVJB) API, might be used. Note, however, that this article does not provide a really good solution to Becky's problem. But it does provide an opportunity to introduce an API (QSPMOVJB) that we have not previously used (and that many are not aware of). Next month, taking a different approach, we'll look at a more-complete solution. Some of the problems with the approach shown this month will be discussed after we review the sample program and API.
The emphasis of this article is on the QSPMOVJB API, so please review the previous articles Monitoring a Job Queue and Monitoring a Job Queue from an RPG Application Program. These articles discuss setting up the environment in which this month's program will run. The one additional step for this month is creating a second *JOBQ, BVINING/JOBQ2. This is the job queue that will be used when we detect a month-end-related job.
The source for the updated SBMDJOBS program follows.
h dftactgrp(*no)
d MovJob pr extpgm('QSPMOVJB')
d FncCtlBlk 4096a const options(*varsize)
d LenFncCtlBlk 10i 0 const
d FmtFntCtlBlk 8a const
d ErrCde likeds(QUSEC)
d RcvDtaQMsg pr extpgm('QRCVDTAQ')
d DtaQName 10a const
d DtaQLib 10a const
d LenDtaRcvd 5p 0
d RcvVar 1a options(*varsize)
d WaitTime 5p 0 const
d KeyOrder 2a const options(*nopass)
d LenKey 3p 0 const options(*nopass)
d Key 4096a options(*varsize :*nopass)
d LenSndrInfo 3p 0 const options(*nopass)
d SndrInfo 4096a options(*varsize :*nopass)
d RmvMsg 10a const options(*nopass)
d LenRcvVar 5p 0 const options(*nopass)
d ErrCde likeds(QUSEC) options(*nopass)
d PrvQJN ds
d PrvJobName 10a
d PrvJobUsr 10a
d PrvJobNbr 6a
d ErrCde ds qualified
d Hdr likeds(QUSEC)
d MsgDta 256a
d Key s 4a inz('0004')
d LenMsg s 5p 0
d NotUsedChr s 1a
/copy qsysinc/qrpglesrc,ejobntfy
/copy qsysinc/qrpglesrc,qspmovjb
/copy qsysinc/qrpglesrc,qusec
/free
RcvDtaQMsg('MYDTAQ' :'BVINING' :LenMsg :EJOQJQN :-1
:'EQ' :%size(Key) :Key :0 :NotUsedChr
:'*YES' :%size(EJOQJQN) :QUSEC);
dow EJOMI00 <> '*STOP';
if ((EJOMI00 = '*JOBNOTIFY') and
(EJOMF00 = '02') and
(EJOQJQN00 = 'MYJOBQ BVINING') and
(%subst(EJOQJN00 :1 :6) = 'MTHEND'));
if PrvJobName <> *blanks;
QSPSJN00 = %subst(EJOQJN00 :1 :10);
QSPSJUN00 = %subst(EJOQJN00 :11 :10);
QSPSJNbr00 = %subst(EJOQJN00 :21 :6);
QSPSIJID00 = *blanks;
QSPTJN = PrvJobName;
QSPTJUN = PrvJobUsr;
QSPTJNbr = PrvJobNbr;
QSPTIJID = *blanks;
MovJob(QSPB0200 :%size(QSPB0200) :'MJOB0200' :ErrCde);
endif;
if (((ErrCde.Hdr.QUSBAvl > 0) and
(ErrCde.Hdr.QUSEI = 'CPF33C1')) or
(PrvJobName = *blanks));
QSPSJN = %subst(EJOQJN00 :1 :10);
QSPSJUN = %subst(EJOQJN00 :11 :10);
QSPSJNbr = %subst(EJOQJN00 :21 :6);
QSPSIJID = *blanks;
QSPTJQN = 'JOBQ2';
QSPTJQL = 'BVINING';
MovJob(QSPB0100 :%size(QSPB0100) :'MJOB0100' :ErrCde);
endif;
if ErrCde.Hdr.QUSBAvl = 0;
PrvQJN = EJOQJN00;
endif;
endif;
RcvDtaQMsg('MYDTAQ' :'BVINING' :LenMsg :EJOQJQN :-1
:'EQ' :%size(Key) :Key :0 :NotUsedChr
:'*YES' :%size(EJOQJQN) :QUSEC);
enddo;
*inlr = *on;
return;
begsr *inzsr;
QUSBPrv = 0;
ErrCde.Hdr.QUSBPrv = %size(ErrCde);
ErrCde.Hdr.QUSBAvl = 0;
endsr;
/end-free
As with the previous SBMDJOBS program, the program uses the Receive Data Queue (QRCVDTAQ) API to receive a job notification message sent by the job notification exit point and then falls into a DOW to process all messages until a *STOP message is sent by a user on the system. Within the DOW, a fourth check has been added to the initial IF statement. For simplicity, I'm assuming that all month-end jobs that are to be routed to another job queue start with a job name of MTHEND. The new check is to determine if the submitted jobs name has MTHEND as the initial six characters. If so, then SBMDJOBS processes the message.
The Move Job API has two capabilities. It can be used to move a given job to the top of a job queue or to move a given job to being after another job on a job queue. The target job queue of the move can be either the job queue the job to be moved is currently on or a different job queue. SBMDJOBS will make use of both the "move to the top" and "move after" capabilities.
Within the DOW, SBMDJOBS uses the data structure PrvQJN (Previous qualified job name) to keep track of the previous month-end job that was moved. When the program processes the first job notification message, the PrvQJN subfield PrvJobName will be blank and the imbedded "if PrvJobName <> *blanks" will be false, giving control to the second imbedded IF (which has the "or (PrvJobName = *blanks))" check). Within this IF, format MJOB0100 of QSPMOVJB is used. MJOB0100 is the format to move a job to the top of a job queue. This format defines six fields: the name of the job to move, the user of the job to move, the number of the job to move, the internal job ID of the job to move, the name of the job queue the job is to be moved to, and the library of the job queue. SBMDJOBS set the first four fields using the job identification information provided in the job notification message and the last two fields to the job queue name JOBQ2 in library BVINING. The QSPMOVJB API is called and the job moves to the top of JOBQ2. SBMDJOBS then saves the qualified name of the job moved to PrvQJN and waits for the next job notification message.
Processing of the next month-end-related job notification message will find the imbedded "if PrvJobName <> *blanks" test to be true. Within this IF, format MJOB0200 of QSPMOVJB is used. MJOB0200 is the format to move a job to right after another job on a job queue. This format defines eight fields: the name of the job to move, the user of the job to move, the number of the job to move, the internal job ID of the job to move, the name of the job to move after, the user of the job to move after, the number of the job to move after, and the internal job ID of the job to move after. SBMDJOBS sets the first four fields using the job identification information provided in the job notification message and the last four fields using the job identification information found in data structure PrvQJN. The QSPMOVJB API is then called to move the job.
This moving of the job may or may not complete successfully. One reason for it to fail would be if the job identified by PrvQJN was no longer on a job queue (it's currently running or has already completed). In this case, the MJOB0200 call to QSPMOVJB will return an error code structure indicating a failure. Specifically, ErrCde.Hdr.QUSBAvl will be non-zero and ErrCde.Hdr.QUSEI will be set to 'CPF33C1' (Job &3/&2/&1 not on job queue. Job not moved.). In this case, SBMDJOBS will fall back to using format MJOB0100 and, as was done for the initial month-end job, move the month-end job to the top of the job queue BVINING/JOBQ2.
Once again, SBMDJOBS then saves the qualified name of the job moved to PrvQJN and waits for the next job notification message.
It's a nice and easy way to move jobs within, or across, job queues.
I mentioned earlier, though, that this approach has some problems/exposures. One is that the Job Notification exit runs asynchronously to the job running the SBMJOB command. While this might be just what you want in some situations, here it introduces the possibility that a submitted month-end job could be placed on the MYJOBQ job queue and start running before the job notification message is received and processed by SBMDJOBS. Therefore, we could have a combination of month-end jobs where some run out of MYJOBQ while others run out of JOBQ2, with the potential that two month-end jobs could be running concurrently due to the two different job queues being used.
A second consideration, and one that is explained in detail in the QSPMOVJB API documentation, is that moving a job can cause a change in the job's priority on the job queue (JOBPTY) and/or a change in the HOLD status of the job. As an example, if job MTHENDX is held on a job queue and then moved after job MTHENDC with MTHENDC having HOLD(*NO), then MTHENDX will be changed to HOLD(*NO) in order for it to be immediately after MTHENDC. As with the asynchronous nature of the job notification exit, this side effect might be just what you want for some situations, but you would really need to know the characteristics and assumptions of the various month-end jobs that might be moved.
Next month, we'll look at another exit capability of the system, one that runs synchronously with the SBMJOB processing, providing a solution that I believe will be much more along the "silver bullet" line Becky's management was hoping for.
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