Wednesday, November 16, 2016

Creating a program to show jobs in message wait

sql rpg with subfile

I do get many requests asking for whole example programs, especially ones with a subfile, rather than just bits and pieces of code that I usually give in these examples. With this in mind this post brings a number of things I have written about before together into one program, which I thought would be an interesting refresher. So here goes...

I was asked to write a program to only show jobs that are in message wait status, and I want to add the ability give the user some options that would allow the user to analyze the error and reply to it.

To summarize what I need to do:

  • Get a list of all jobs in message wait status
  • Load that information into a subfile to display
  • Allow user to select one subfile record and then see the job's information

I have written about all of these in previous posts, so I will be referring to those posts from this one.

Let me get started with the definition section of the RPG program:

001  **free
002  ctl-opt option(*nodebugio:*srcstmt:*nounref:*showcpy)
              dftactgrp(*no) ;

003  dcl-ds Pgm extname('RPG4DS') psds qualified
004  end-ds ;

005  dcl-f CHKMSGWD workstn indds(Dspf) sfile(SFL01:Z1RRN)
                     extfile('MYLIB/CHKMSGWD') ;

006  dcl-ds Dspf qualified ;
007    Exit ind pos(3) ;
008    Refresh ind pos(5) ;
009    DspSysOprMsg ind pos(7) ;

010    SflDspCtl ind pos(30) ;
011    SflDsp ind pos(31) ;

012    ProtectOption ind pos(40) ;
013  end-ds ;

014  dcl-ds Ds qualified dim(50) ;
015    JobName char(28) ;
016    Subsystem char(10) ;
017    User char(10) ;
018    JobType char(3) ;
019    JobStatus char(4) ;
020    Function char(10) ;
021    CpuTime packed(7) ;
022  end-ds ;

023  dcl-s String varchar(200) ;
024  dcl-s NbrOfRows packed(5) inz(%elem(DS)) ;
025  dcl-s RowsFetched packed(5) ;

026  Z1SCREEN = %trimr(Pgm.ProcNme) + '-1' ;

Line 1: The **FREE tells the compiler, and us, that this is written in totally free RPG.

Line 2: These are my standard control options, I use the OPTION keyword to define my compile options, and as I will be using procedures I specify DFTACTGRP(*NO).

Lines 3 and 4: I always use an externally described data structure to define the program status data structure. The QUALIFIED means that all of the data structure subfields have to be qualified with the data structure name.

Line 5: Here is the only file definition in the program, the display file. By stating it is a WORKSTN file I do not need to use the USAGE keyword. INDDS means that I am using an indicator data structure. SFILE gives the relative record field for the subfile. I have defined EXTFILE as this gives the library the display file is in. By using the EXTFILE the program can be called with needing the library the display file is in to be in the library list. I only use this for "utility" programs like this, I do not use it for display files in "application" programs.

Lines 6 – 13: Here is the indicator data structure for the display file. I hate using number indicators as they don't tell you what they mean. By using an indicator data structure I can give all of the indicators used in the display file a meaningful name. For example: Dspf.SflDsp tells me how this indicator is used, *IN31 does not.

Lines 14 – 22: This data structure array is what I will be using when I get the data, more on that later.

Line 23: The only thing of note with this line is that it is defined as a variable length character.

Line 24: This variable is initialized with a number that is the same as the number of elements in the data structure array. If I ever change the number of elements in the array I will not have to remember to change this variable too.

Line 26: By all means this is not a definition, but I am including here as it gets the program name from the program data structure and moves it to the program name field in the display file.

In the next piece of code I call the procedures to get the data and load the subfile.

027  GetData() ;
028  LoadSubfile() ;

I use, what I call, "open" subprocedures rather than subroutines. The difference between an "open" subprocedure and "closed" one is that the "open" lacks the procedure interface. This allows all of the variables defined in the main body of the program to be available to the "open" subprocedure, but any variables I define within the subprocedures are not available to the main body of the program.

Onto the first "open" subprocedure, which gets the data of the jobs in message wait status.

050  dcl-proc GetData ;
051    clear Ds ;

052    exec sql DECLARE C0 CURSOR FOR
                        => '*ALL')) A
056               WHERE JOB_STATUS = 'MSGW'
057               ORDER BY ORDINAL_POSITION ;

058    exec sql OPEN C0 ;

059    exec sql FETCH C0 FOR :NbrOfRows ROWS
                 INTO :Ds ;

060    exec sql GET DIAGNOSTICS :RowsFetched = ROW_COUNT ;

061    exec sql CLOSE C0 ;
062  end-proc ;

Line 50: All procedures start with a DCL-PROC, and end with an END-PROC, see line 62.

Line 51: I clear the data structure array that will be receiving the data as I don't know how many elements will be used and I don't want elements with data left over from the previous time it was loaded when I refresh.

Lines 52 – 57: Fortunately I do not have to mess around with APIs as the information about all the active jobs is available as a DB2 Table function, ACTIVE_JOB_INFO. I can just Select the columns/fields and the rows/records I want from this Table function. I am ordering/sorting it by the ordinal position, which is a unique number for each job with the lowest number being the oldest job.

Line 58: I open the cursor.

Line 59: This line is a fantastic "time saver" in terms of performance. I am getting more than one row in just one Fetch. The number of rows I am getting is held in the NbrOfRows variable, which is the number of number of elements in the data structure array. So in one I/O I am getting 50 rows, think of the time savings if I was to use a bigger value. But in this case I think 50 is more than enough, as I doubt if this IBM i ever has that many errors at one time. The fetched rows are loaded in the Data structure array, Ds.

Line 60: Later in this program I need to know how many elements in the array are used. By retrieving the number of rows fetched I have that number in the variable RowsFetched.

Line 61: I am all done with the cursor so I close it.

When this procedure ends all the data I need to load the subfile is held in the data structure array. This is what the next subprocedure, LoadSubfile, does. But before I explain the code in there it is best to give the DDS code for the display file.

Let me start with the file level keywords.

01  A                                      DSPSIZ(24 80 *DS3)
02  A                                      PRINT
03  A                                      INDARA
04  A                                      ERRSFL
05  A                                      CA03(03 'F3=Exit')
06  A                                      CA05(05 'F5=Refresh')
07  A                                      CA07(07 'F7=DspMsg *Sysopr')

There are no surprises there. The INDARA, line 3, is the "other end" of RPG's indicator data area. The error subfile, line 4, means that the display file handles the error subfile rather than I having to write errors to the message subfile.

The subfile record format is straight forward.

08  A          R SFL01                     SFL
09  A            Z1RRN          3S 0H
10  A            Z1OPT          1A  B  7  2
11  A  40                                    DSPATR(ND PR)
12  A            JOBNAME       27   O  7  4
13  A            SUBSYSTEM     10   O  7 32
14  A            USER          10   O  7 43
15  A            JOBTYPE        3   O  7 54
16  A            JOBSTATUS      4   O  7 58
17  A            FUNCTION      10   O  7 63
18  A            CPUTIME        7Y 0O  7 74EDTCDE(Z)

The only thing to note is that for the Z1OPT field, line 10, when indicator 40 is on, line 11, the field is protected from input and non-displayed.

While the code for the control format is a lot longer than that of the subfile format, most of it is due to the formatting of the layout of the headings on the screen.

19  A          R CTL01                     SFLCTL(SFL01)
20  A                                      SFLSIZ(0999)
21  A                                      SFLPAG(0015)
22  A                                      OVERLAY
23  A  31                                  SFLDSP
24  A  30                                  SFLDSPCTL
25  A N30                                  SFLDLT
26  A  30                                  SFLEND(*MORE)
27  A                                  1  2USER
28  A                                      COLOR(BLU)
29  A                                  1 31'R P G P G M . C O M'
30  A                                      DSPATR(HI)
31  A                                  1 63TIME
32  A                                      COLOR(BLU)
33  A                                  1 72DATE
34  A                                      EDTCDE(Y)
35  A                                      COLOR(BLU)
36  A            Z1SCREEN      12A  O  2  2COLOR(BLU)
37  A                                  2 35'Jobs in MSGW'
38  A                                      DSPATR(HI)
39  A                                  2 72SYSNAME
40  A                                      COLOR(BLU)
41  A                                  3  2'                                  -
42  A                                                                         -
43  A                                               '
44  A                                      COLOR(BLU)
45  A                                      DSPATR(UL)
46  A                                  4  2'1=DSPJOB   2=WRKACTJOB user   3=Se-
47  A                                      nd break msg'
48  A                                      COLOR(BLU)
49  A                                  5 54'Job Job                 CPU'
50  A                                      DSPATR(HI)
51  A                                  6  2'S Job name                    Subs-
52  A                                      ystem  User       Typ Sts  Function-
53  A                                            time'
54  A                                      DSPATR(UL)
55  A                                      DSPATR(HI)

Line 19: CTL01 is the control format for the subfile SFL01.

Line 20: The subfile will have 999 records.

Line 21: 15 records will display on the screen at any one time.

Lines 20 and 21 give away that this is a "load all" type subfile.

Line 32: When *IN31 the subfile record format is displayed. As we are using an indicator area data structure *IN31 will be known by a real name in the RPG.

Line 24 – 26: *IN30 is being used to do a variety of tasks. When it is off it will delete the subfile. When it is on it will display the control record format and More... and Bottom to indicate that there is more than one page of the subfile.

I always like my screens to show the user, date, time, system, and program/screen id. The first three I can use Display file keywords. For user I can use the keyword USER (line 27), date DATE (line 33), time TIME (line 31), system SYSNAME (line 39), the only one I cannot get is the program/screen name (line 36) which I make in my RPG program.

The last record format, FOOT01, just displays which function keys can be used.

56  A          R FOOT01
57  A                                 23  3'F3=Exit   F5=Refresh   F7=DspMsg -
58  A                                      SysOpr'
59  A                                      COLOR(BLU)

Back to the RPG program's subprocedure LoadSubfile. While it looks long it is simple.

063  dcl-proc LoadSubfile ;
064    Dspf.SflDspCtl = *off ;
065    Dspf.SflDsp = *off ;
066    write CTL01 ;
067    Dspf.SflDspCtl = *on ;
068    Dspf.SflDsp = *on ;

069    Z1OPT = ' ' ;

070    if (RowsFetched = 0) ;
071      clear SFL01 ;
072      JOBNAME = 'Hooray, no errors here' ;
073      Z1RRN = 1 ;
074      Dspf.ProtectOption = *on ;
075      write SFL01 ;
076      return ;
077    endif ;

078    Dspf.ProtectOption = *off ;

079    for Z1RRN = 1 to RowsFetched ;
080      JOBNAME = Ds(Z1RRN).JobName ;
081      SUBSYSTEM = Ds(Z1RRN).Subsystem ;
082      USER = Ds(Z1RRN).User ;
083      JOBTYPE = Ds(Z1RRN).JobType ;
084      JOBSTATUS = Ds(Z1RRN).JobStatus ;
085      FUNCTION = Ds(Z1RRN).Function ;
086      CPUTIME = Ds(Z1RRN).CpuTime ;

087      write SFL01 ;
088    endfor ;
089  end-proc ;

Lines 64 – 68: This is the part where I am deleting the existing subfile and replacing it will another new one.

Line 70 – 77: This is what I am going to do to the subfile if no rows were retrieved by the Fetch. I am going to write a message to the subfile that there are no errors, line 72, to the subfile and protect the option field from input by using the indicator Dspf.ProtectOption, which is *IN44 is the display file. To quit the subprocedure I use the return operation code, line 76, which I would want to do here as no rows were retrieved.

From this point on the subprocedure is very simple…

Lines 79 – 88: This is where I use the RowsFetched as I only want to perform the For loop for the same number of times as rows I fetched. From then on I am just moving the values from the data structure array subfields to the fields in the subfile record format, and then writing a subfile record.

Control returns to the main body of the program. From here all I do is to show the display file.

029  write FOOT01 ;

030  dow (1 = 1) ;
031    exfmt CTL01 ;

032    if (Dspf.Exit) ;
033      leave ;
034    elseif (Dspf.Refresh) ;
035      GetData() ;
036      LoadSubfile() ;
037    elseif (Dspf.DspSysOprMsg) ;
038      String = 'DSPMSG MSGQ(*SYSOPR)' ;
039      ExecuteCommand() ;
040    else ;
041      ReadSubfile() ;
042    endif ;
043  enddo ;

044  *inlr = *on ;

Line 29: I write bottom part of the display file as I will be using EXFMT with the control record format.

Line 30 - 43: The user remains in this Do loop until they press F3 to exit the program.

Line 31: I EXFMT the control format and wait for the user to do something.

If there were error messages the screen would look like:

SIMON                       R P G P G M . C O M             TT:TT:TT DD/DD/DD
CHKMSGW-1                        Jobs in MSGW                         DEV730
1=DSPJOB   2=WRKACTJOB user   3=Send break msg
                                                    Job Job                 CPU
S Job name                    Subsystem  User       Typ Sts  Function      time
_ 304922/ADMIN/WA1045C        QBATCH     ADMIN      BCH MSGW WA0045C        652
_ 380832/SIMON/TESTCLP        QPGMR      SIMON      BCH MSGW TESTCLP          7

 F3=Exit   F5=Refresh   F7=DspMsg SysOpr

If there were no errors:

 SIMON                       R P G P G M . C O M             TT:TT:TT DD/DD/DD
CHKMSGW-1                        Jobs in MSGW                         DEV730
1=DSPJOB   2=WRKACTJOB user   3=Send break msg
                                                    Job Job                 CPU
S Job name                    Subsystem  User       Typ Sts  Function      time
   Hooray, no errors here

Next comes an IF-ELSEIF group. I could have used a Select group, but it is just a question of personal preference, and I prefer this way.

Lines 32 and 33: Dspf.Exit means that F3 was pressed, and the DO loop is exited.

Lines 34 – 36: Dspf.Refresh means that the F5=Refresh was pressed, data is fetched and the subfile loaded with it.

Lines 37 – 39: Dspf.DspSysOprMsg means that F7 was pressed to display the system operator messages. I move the command to be executed into the variable String, and then execute the subprocedure ExecuteCommand, no prizes for guessing what that subprocedure does.

Lines 40 and 41: If none of the above Ifs were executed the subprocedure ReadSubfile will be executed.

For all of you who were not able to guess what the subprocedure ExecuteCommand does it executes the command in String by calling the QCMDEXC API.

130  dcl-proc ExecuteCommand ;
131    dcl-pr QCMDEXC extpgm ;
132      *n char(200) options(*varsize) const ;
133      *n packed(15:5) const ;
134    end-pr ;

135    if (String <> ' ') ;
136      QCMDEXC(String:%len(%trim(String))) ;
137    endif ;
138  end-proc ;

Lines 131 – 134: This is the procedure definition to call the program QCMDEXC. I can tell it is a program as the EXTPGM keyword is present on line 131. As I called the procedure definition the same name as the program I do not have to give the program's name, just the EXTPGM.

Line 132: I don't both to give names to the parameters in the procedure definitions. This one will contain the commands, as the commands' length can vary I define it with the OPTIONS<(*VARSIZE).

Line 136: When there is a value in String I call QCMDEXC to execute it. The first parameter is the variable String, the second is the length of the text within String. There is no need for me to use another variable for that, I can just calculate it in the second parameter.

The next subprocedure reads the subfile to determine if the user put something next to one of the subfile's records, and then executes that command.

100  dcl-proc ReadSubfile ;
101    dow (1 = 1) ;
102      readc SFL01 ;
103      if (%eof) ;
104        leave ;
105      endif ;

106      if (Z1OPT = '1') ;
107        String = 'DSPJOB JOB(' + %trimr(Ds(Z1RRN).JobName) + ') +
                              OUTPUT(*)' ;
108        ExecuteCommand() ;
109      elseif (Z1OPT = '2') ;
110        String = 'WRKUSRJOB USER(' + %trimr(Ds(Z1RRN).User) + ') +
                                     STATUS(*ACTIVE)' ;
111        ExecuteCommand() ;
112      elseif (Z1OPT = '3') ;
113        SendMessage() ;
114      endif ;

115      Z1OPT = ' ' ;
116      update SFL01 ;
117    enddo ;
118  end-proc ;

Line 102: READC is the operation code to read for changed records in a subfile.

Lines 106 - 108: If "1" was entered in the option field then the Display Job command is built for the user and placed in the variable String. By calling the ExecuteCommand the command in String will be executed.

Lines 109 - 111: This is part of the program I would like your help for. I wanted a simple (easy) way to display the error message. I looked many commands and could not find one to do what I want. Do you know of a way to display an error message for a job from another? If you do please let me know in the comments section at the bottom of this post.

Until I find something better I am using the Work User Job command to allow the user to display the job and answer the message.

Lines 112 and 113: I wanted to give the user the ability to send a message to the person with the error. Perhaps to say something like: "Your job has errored, stop submitting the same job again and again", etc. I prefer to send messages via the QEZSNDMG API, I put the call to that API in its own subprocedure, SendMessage.

Lines 115 and 116: When all the processing has happened for whatever choices the user had made the option field is cleared and the subfile updated. If I do not do this the modified data flag, that READC identifies, is not cleared, the next time this subprocedure is called the subfile's records that were processed before will be identified to be processed again.

The final subprocedure I need to discuss is the SendMessage. As I discussed how to use this in a previous post about sending break messages I am only going to describe this in the briefest manner.

150  dcl-proc SendMessage ;
151    dcl-pr QEZSNDMG extpgm  ;
152      *n char(10) const ;
153      *n char(10) const ;
154      *n char(300) options(*varsize) const ;
155      *n int(10) const  ;
156      *n char(10) const ;
157      *n int(10) const ;
158      *n int(10) const ;
159      *n int(10) const ;
160      *n char(8) ;
161      *n char(1) const ;
162      *n char(20) const ;
163      *n char(4) const ; 
164      *n int(10) const ;
165    end-pr ;

166    dcl-s RtnError char(8) ;

167    QEZSNDMG('*INFO':'*BREAK':' ':1:
                 1:0:0:RtnError:'Y':' ':'*USR':0) ;
168  end-proc ;

Lines 151 – 165: These are the parameters to be passed to the API QEZSNDMG. Notice how the parameter on line 160 does not have the CONST, that the others do, as this is a returned parameter.

Line 166: I need a variable for that returned parameter, even though I am not going to do anything with it.

Line 167: Then only thing to note in this call to the API is that I am passing the user id from the subfile record selected. When the send message screen is displayed the user id will appear in the "Send to" field.


So there we have it, a complete display file program that does something useful. This is a program is more than just an example, the operators at my employer now use this program to monitor for jobs in error on the production servers. You could use it too on your IBM i.


This article was written for IBM i 7.3, and while some parts will not work for earlier releases too other parts will you just need to change the RPG code.


  1. I am surprised you are not using the system for your command.
    dcl-pr GoCmd INT(10) EXTPROC('system');
    This is another great post. Have your editor scan it again you have a couple typo's but nothing we cant figure out...thanks

  2. Personally I prefer to use QCMDEXC.

    I know there is a whole debate about which is better. And I have written about SYSTEM() too.

    Thank you for the heads up about the spelling errors. I think I have got them all now.

  3. think the same as Hutch in my case for reasons of scalability. Although there is certainly a debate on this matter I prefer the interest of customers in relation to the version of the operating system that they use, I believe for now it is more popular among programmers to think of the term "QCMDEXC" greetings

  4. can you provide an link where all of the code can be downloaded

    1. Alas, there is not a place to go to download the code shown. You could easily just copy-n-paste from the posts in Notepad, and then upload that to your IBM i.

  5. Don't know where to put this , so it goes here. I believe you only need to put the parts of the code needed for what your trying to show and not a completed working pgm. Like a pop up window showing group jobs. Do you need to show how to get group jobs working? So no, just the main stuff. If you need the whole thing then offer a Jim Sloan disk.

  6. @Simon Hutchinson - Same task was accomplished by writing down to the spool and reading the spool file for MSGW, But we had to run the job in delay(500) so the every five minutes the job created a spool and then reads through it. How is the your code going to be differentiate from the approach mentioned . Also please comment performance wise.

  7. Your method of creating a spool file and then copying it to a physical file so it can be read, is going to be a lot slower than the method I have described above, where you get the data straight away in a usable form.

    Also using a multiple row fetch is a lot faster, many records in one I/O operation, than reading a file multiple times with a RPG READ operation, one record per I/O.

    As for having a DLYJOB, or maybe a sleep(), it can easily included into the code I have given.

  8. Simon, At server version V7R1M0 code failed to compile with following errors.
    SQL0104 30 62 Position 61 Token => was not valid. Valid tokens: ) ,.
    SQL5011 30 69 Position 35 Host structure array DS not defined or not

  9. I would need to see more of your code than just the error messages. It could be that the Table function is not available at the version of 7.1 you have on your IBM i.
    I would STRSQL and try a simple SQL Select using this Table function to test that it is there.

    1. At v7.1 with TR10 installed UDTF ACTIVE_JOB_INFO its supported but with some limitations.
      this SQL select runs at v7r1:
      JOB_STATUS from
      table(QSYS2.ACTIVE_JOB_INFO('NO','','','')) a

  10. Yes, probably you are correct. I used STRSQL
    above says ACTIVE_JOB_INFO in QSYS2 type *N not found.

    But same is working fine at V7R3M0 IBMi machine.

    Thank you so much Simon.

    1. You are missing part of what I gave in my example:
      => '*ALL'


  11. Yes it was just for an example.

    I copied all from your example and created a program on V7R3M0 machine. Its is working fine. Thank you.

  12. Same for me, it's up and keeps working without a problem. I've tested all the option now also.

    Thanks so much! I loved the explanations of each line.

  13. Embedded sql is the way to go with subfiles! Great flexibility for the search criteria in the subfile-control format.

  14. Excellent stuff Simon.
    I think you're right, I think this would be a better method to use RE our conversation on your other post.
    Perfect, thanks :)

  15. Many thanks for that great post.

    Deleting line 056 ("WHERE JOB_STATUS = 'MSGW'") I would expect to get all active jobs. In STRSQL it works. But from RPG I get only one job/record into :DS.

    What is my mistake?

    1. I would guess you have a null in a column and you are not handling it.

      Run your program in debug with a break point immediately after the Fetch statement. Look for the SQLCOD and the SQLCA they will give you an idea of what is "wrong".

    2. Yes Simon. That's it! Many many thanks.

      "eval sqlca" pointed me directly to "function" (error -305). So I changed the SQL from "function" to "IFNULL(FUNCTION,''-'')" and now it works as expected. :-)


  16. I wrote the sql program to fetch records from file and load the subfile

    Ur explanation is great

  17. Hi Simon,

    Is it possible to send email alerts if a job goes to "MSGW" state.

    Sunil Boggavarapu

    1. Of course it is.

      You can use the logic described above to check on the job every so many seconds. If it is in MSGW you can send an email using the SNDSMTPEMM command.

      (Thinks... perhaps this would make a good new post)


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