02
Sat, Nov
2 New Articles

The CL Corner: More-Flexible Testing of Your CL Program Error-Handling

CL
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

Use message replacement data along with the Command Analyzer Retrieve exit point.

 

In our last column, "Testing Your CL Program Error-Handling," we looked at a rather simplistic SNDESCAPE exit program and noted several assumptions in how the program is written:

  • There is a separate exit program for each command that needs to be tested.
  • There is no need to test error-handling in the MONESCAPE program that is based on replacement data within the CPF414E message.
  • The program MONESCAPE is the only program in the current job that runs the DONOTHING command (otherwise, the SNDPGMMSG command will fail).

 

In this column, we will address the first two assumptions. In a subsequent column, we will look at how to avoid the third assumption.

 

Currently, the SNDESCAPE exit program does not check to see what command is running. It simply sends the escape message CPF414E (if the signed-on user is VININGTEST) whenever the program runs. Due to this implementation, a separate version of the exit program is needed for each command and escape message combination that you might want to test in terms of proper monitoring of various messages. The Command Analyzer Retrieve exit point does, however, provide information on what command is causing the exit program to run. This information is available in the parameter passed to the exit program, and we will look at this additional data now. Here is the source for an updated SNDESCAPE program:

 

 

Pgm        Parm(&Parm)                                          

Dcl        Var(&Parm)     Type(*Char) Len(38)                  

 Dcl        Var(&CmdName) Type(*Char) Stg(*Defined) +          

              Len(10) DefVar(&Parm 29)                         

                                                                

Dcl        Var(&User)     Type(*Char) Len(10)                  

                                                               

RtvJobA    User(&User)                                         

                                                                

If         Cond(&User *Eq ViningTest) Then(Do)                 

           Select                                              

              When Cond(&CmdName = DONOTHING) Then(Do)         

                   SndPgmMsg MsgID(CPF414E) MsgF(QCPFMsg) +     

                     ToPgmQ(*Same (MonEscape)) MsgType(*Escape)          

                   EndDo                                        

              When Cond(&CmdName = XXX) Then(Do)                

                   SndPgmMsg MsgID(CPF415B) MsgF(QCPFMsg) +     

                     ToPgmQ(*Same (MonEscape)) MsgType(*Escape) 

                   EndDo                                        

              EndSelect                                         

           EndDo                                                

EndPgm                                                 

 

The single parameter passed by the Retrieve exit point is a structure providing quite a bit of information about the command running. The documentation for this structure can be found here. Of interest to us today is the name of the command being run. This can be found in positions 29 through 38 of the structure and is declared by this version of SNDESCAPE as variable &CmdName. Note that &CmdName is declared as *Defined over the structure &Parm. This use of Stg(*Defined) means that this version of the program requires that your system be at V5R4 or later. Earlier releases of the operating system can also check to see what command is being used but would require that you substring (%sst) the value of &CmdName out of the &Parm parameter. The %sst approach works but is less efficient in terms of program execution. Using *Defined storage is also much more self-documenting, to my mind anyway, in terms of understanding what the program is doing. To compile SNDESCAPE, you would still use CRTBNDCL VINING/SNDESCAPE.

 

As we are not interested in any of the information found beyond the command name, SNDESCAPE defines &Parm as being only 38 bytes in length, though a larger value (such as 76, which would match the exit point documentation) will do no harm. With the addition of &CmdName and the SELECT group, SNDESCAPE will now send CPF414E if the user VININGTEST is running the command DONOTHING and CPF415B if VININGTEST is running the command XXX. This is assuming that you also create the command XXX using the command CRTCMD CMD(VINING/XXX) PGM(VINING/DONOTHING) and register the SNDESCAPE program with the Command Analyzer exit point with this command:

 

 

ADDEXITPGM EXITPNT(QIBM_QCA_RTV_COMMAND) FORMAT(RTVC0100) PGMNBR(2)

   PGM(VINING/SNDESCAPE) PGMDTA(*JOB 20 'XXX       VINING')

 

(Note that there are seven blank spaces between the XXX and VINING. The command name must be blank padded to a full 10 characters when registering the exit program for a command.)

 

So we can now have one exit program sending various escape messages in support of testing different commands. We do, however, still have the limitation of no message replacement data. Furthermore, the commands must be running in a program named MONESCAPE (due to the TOPGMQ parameter of the SNDPGMMSG command used by SNDESCAPE).

 

Let's now take on the message replacement data aspect. Here is an updated SNDESCAPE that provides a device name of MYDEVICE when sending CPF414E:

 

 

Pgm        Parm(&Parm)                                          

Dcl        Var(&Parm)     Type(*Char) Len(38)                   

 Dcl        Var(&CmdName) Type(*Char) Stg(*Defined) +           

              Len(10) DefVar(&Parm 29)                          

                                                                

Dcl        Var(&User)     Type(*Char) Len(10)                   

                                                                

Dcl        Var(&Dta_414E) Type(*Char) Len(58)                   

 Dcl        Var(&Device)   Type(*Char) Stg(*Defined) +           

              Len(10) DefVar(&Dta_414E 41)                       

                                                                

RtvJobA    User(&User)                                          

                                                                 

If         Cond(&User *Eq ViningTest) Then(Do)                  

           Select                                               

              When Cond(&CmdName = DONOTHING) Then(Do)          

                   ChgVar Var(&Device) Value(MyDevice)         

                   SndPgmMsg MsgID(CPF414E) MsgF(QCPFMsg) +    

                     MsgDta(&Dta_414E) ToPgmQ(*Same +          

                     (MonEscape)) MsgType(*Escape)             

                   EndDo                                        

              When Cond(&CmdName = XXX) Then(Do)               

                   SndPgmMsg MsgID(CPF415B) MsgF(QCPFMsg) +    

                     ToPgmQ(*Same (MonEscape)) MsgType(*Escape)

                   EndDo                                        

              EndSelect                                        

           EndDo                                               

EndPgm

 

 

The changes to SNDESCAPE are the following additions:

 

 

  • The structure &Dta_414E is declared. This structure matches the replacement data defined for CPF414E with the length determined by using DSPMSGD RANGE(CPF414E), selecting option 2, and then adding up the storage for the various fields that are defined.
  • The field &Device is declared. This field matches replacement variable &5 of CPF414E with the purpose and size determined by using options 1 and 2 of the previous DSPMSGD output. Notice that &Device is declared as being *Defined over the storage of &Dta_414E.
  • Within the WHEN group, the variable &Device is set to a value of MyDevice. This variable, as a portion of the larger &Dta_414E structure, is then sent as replacement data with the CPF414E escape message.

 

To complement this change to program SNDESCAPE, we also make the following changes to MONESCAPE:

 

 

 Pgm                                                    

                                                       

Dcl        Var(&X) Type(*Char) Len(50)                 

Dcl        Var(&Dta_414E) Type(*Char) Len(58)          

 Dcl        Var(&Device) Type(*Char) Stg(*Defined) +   

              Len(10) DefVar(&Dta_414E 41)             

Dcl        Var(&LenRplDta) Type(*Dec) Len(5 0) +       

              Value(58)                                

                                                        

ChgVar     Var(&X) Value('A One')                      

                                                       

XXX                                                    

MonMsg     MsgID(CPF415B) Exec( +                       

             Chgvar Var(&X) +                          

               Value(&X *TCat ', and a Two'))          

                                                      

DoNothing                                             

MonMsg     MsgID(CPF414E) Exec(Do)                    

           RcvMsg MsgType(*Last) MsgDta(&Dta_414E) +  

             MsgDtaLen(&LenRplDta)

           If Cond(&Device = MyDevice) Then( +        

              Chgvar Var(&X) +                        

                Value(&X *TCat ', and a 414E'))       

           Else Cmd(ChgVar Var(&X) +                  

              Value(&X *TCat ',...'))                 

           EndDo                                      

                                                       

ChgVar     Var(&X) +                                  

             Value(&X *TCat ', and a Three')          

SndPgmMsg  Msg(&X)                                    

                                                      

Return                                                 

EndPgm         

 

 

These are the additions to MONESCAPE:

 

  • We declare the structure &Dta_414E with the subfield &Device, as we did for SNDESCAPE.
  • We declare the variable &LenRplDta to represent the length of the &Dta_414E structure.
  • In the MONSMG MSGID(CPF414E) associated with the DONOTHING command, we use the Receive Message (RCVMSG) command to receive the last message sent to our program. When receiving the message, we ask for &LenRplDta bytes of replacement data to be returned to the &Dta_414E structure.
  • Within the same MONMSG group, we test the value of variable &Device. If it's equal to the constant MyDevice, the program modifies variable &X with ',and a 414E'; otherwise, variable &X is modified with ',...'.

Both MONESCAPE and SNDESCAPE are now quite a bit more useful in terms of being able to test application changes in CL programs. SNDESCAPE can be used to test proper error-handling within MONESCAPE by selectively sending escape messages and, when appropriate, replacement data associated with the escape messages. We continue to have the limitation, though, that SNDESCAPE is hard-coded to only test a program named MONESCAPE. In the next column, we'll see how to eliminate this limitation.

 

More CL Questions?              

Wondering how to accomplish a function in CL? Send your CL-related questions to me at This email address is being protected from spambots. You need JavaScript enabled to view it.. I'll try to answer your burning questions in future columns.

 

Bruce Vining

Bruce Vining is president and co-founder of Bruce Vining Services, LLC, a firm providing contract programming and consulting services to the System i community. He began his career in 1979 as an IBM Systems Engineer in St. Louis, Missouri, and then transferred to Rochester, Minnesota, in 1985, where he continues to reside. From 1992 until leaving IBM in 2007, Bruce was a member of the System Design Control Group responsible for OS/400 and i5/OS areas such as System APIs, Globalization, and Software Serviceability. He is also the designer of Control Language for Files (CLF).A frequent speaker and writer, Bruce can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it.. 


MC Press books written by Bruce Vining available now on the MC Press Bookstore.

IBM System i APIs at Work IBM System i APIs at Work
Leverage the power of APIs with this definitive resource.
List Price $89.95

Now On Sale

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: