29
Fri, Nov
0 New Articles

TechTalk: Using Data Queues for Automatic Screen Painting

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

From: Alan Baldwin, Jr.

To: All

I am working on a project to do automatic updates to several screens, and I'm hoping someone else has run into the problem I'm having. We have up to 40 people taking calls and using a program to write call records to the same file. We also have up to 15 dispatchers running the same program to view this file. The program reads the call records file and fills a subfile with call records depending on what the dispatcher has chosen to see. The way the program works now, the dispatcher has to hit a function key to refresh the screen with any new calls.

I have been attempting to do automatic refresh using data queues. I'm having a problem enabling multiple dispatchers to read from the same data queue. Because records received from a data queue are removed from the data queue, only one dispatcher gets the record.

Does a data queue have to be associated with the program's screen file for the program to be able to wait for input from the screen or the keyboard?

From: Art Tostaine

To: Alan Baldwin, Jr.

I've been writing almost the exact same application. Instead of calls, we have radio frequency (RF) units scanning trailers and tractors into the yard, and we want to have an airport-type arrivals screen constantly refreshing. We could have up to five dispatch screens around the building. I do it just as you described.

I was able to get our system to work. The technique really isn't that difficult, it's just that none of it is written down in any one place. What follows is an explanation of how I currently have it working with automatic update. Figures 6-8 contain pieces of the code related to the data queue technique.

6 contains the RPG code that sends the data to the data queue. In our circumstance, we work with RF. Each truck we dispatch to has its own frequency, and each dispatcher watches two to three frequencies. When dispatchers log in, I write their device names and what frequencies they have to a file (more on this later). The code in 6 reads the Emergency Road Service Frequency (ERSFREQ) and sends just the frequency to all dispatchers in the file that match that frequency.

Figure 6 contains the RPG code that sends the data to the data queue. In our circumstance, we work with RF. Each truck we dispatch to has its own frequency, and each dispatcher watches two to three frequencies. When dispatchers log in, I write their device names and what frequencies they have to a file (more on this later). The code in Figure 6 reads the Emergency Road Service Frequency (ERSFREQ) and sends just the frequency to all dispatchers in the file that match that frequency.

Next, I use a CL program (see 7) to call the dispatcher's program. I create a non-keyed data queue (keyed data queues are not supported) using the name of the device. The program does some error checking to see if the data queue already exists. Then the program overrides the display file to associate the data queue with it. Using this method, dispatchers get their own data queues!

Next, I use a CL program (see Figure 7) to call the dispatcher's program. I create a non-keyed data queue (keyed data queues are not supported) using the name of the device. The program does some error checking to see if the data queue already exists. Then the program overrides the display file to associate the data queue with it. Using this method, dispatchers get their own data queues!

8 shows a segment of the RPG code for the program used by the dispatchers. The first three statements clear the data queue because I just updated the screens. I then wrote the subfile that displays the outstanding calls. Setting on indicator 89 activates the INVITE keyword in the display file. Next, I wrote the KEYS1 record. By calling the QRCVDTAQ program, the RPG program waits (WAIT = -1) until it receives input from the screen or the data queue. (If you receive something from the data queue, write KEYS1 again with indicator 89 off to turn off the INVITE keyword, and then update the subfile. Otherwise, read KEYS1 and proceed as normal.)

Figure 8 shows a segment of the RPG code for the program used by the dispatchers. The first three statements clear the data queue because I just updated the screens. I then wrote the subfile that displays the outstanding calls. Setting on indicator 89 activates the INVITE keyword in the display file. Next, I wrote the KEYS1 record. By calling the QRCVDTAQ program, the RPG program waits (WAIT = -1) until it receives input from the screen or the data queue. (If you receive something from the data queue, write KEYS1 again with indicator 89 off to turn off the INVITE keyword, and then update the subfile. Otherwise, read KEYS1 and proceed as normal.)

This is my first attempt with data queues. No "real" data is being sent from one program to another. It's just a message saying, "Hey, I wrote a record to the file. Update your screen."

By the way, two articles helped me a lot: "Line Up for Data Queues," MC, May 1992, and "Event-driven Programming with Data Queues," MC, December 1993.


TechTalk: Using Data Queues for Automatic Screen Painting

Figure 6: RPG Code for Sending Data to Data Queue

 *. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 I DS I 1 7 DQDATA I 1 5 DQRQST I 6 70DQFRQ C*================================================================ C* Write records to data queues C CLRAFQ SETLLERSFREQ C CLRAFQ READEERSFREQ 61 C *IN61 DOWEQ*OFF C CALL 'QSNDDTAQ' C PARM DEVNAM C PARM DQLIB C PARM LEN C PARM DQDATA C CLRAFQ READEERSFREQ 61 C ENDDO *. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 
TechTalk: Using Data Queues for Automatic Screen Painting

Figure 7: CL Program to Create Data Queue Named as Device

 PGM /* */ DCL VAR(&USRDEV) TYPE(*CHAR) LEN(10) RTVJOBA JOB(&USRDEV) CRTDTAQ DTAQ(AAAPROD/&USRDEV) MAXLEN(100) TEXT('ERS + Data Queue') AUT(*ALL) MONMSG MSGID(CPF9870) EXEC(GOTO CMDLBL(CLRQUE)) GOTO SKPCLR /* */ CLRQUE: DLTDTAQ DTAQ(AAAPROD/&USRDEV) CRTDTAQ DTAQ(AAAPROD/&USRDEV) MAXLEN(100) TEXT('ERS + Data Queue') AUT(*ALL) /* */ SKPCLR: OVRDSPF FILE(SERS998) TOFILE(AAAPROD/SERS998) + DTAQ(AAAPROD/&USRDEV) CALL PGM(AAAPROD/ERS998) DLTDTAQ DTAQ(AAAPROD/&USRDEV) ENDPGM 
TechTalk: Using Data Queues for Automatic Screen Painting

Figure 8: Partial RPG Code to Receive Input from Data Queue

 *. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 C CALL 'QCLRDTAQ' C PARM STJOB C PARM DQLIB C WRITESFLCTL1 C BADRID TAG C SETON 89 C WRITEKEYS1 C*===================================================== C CALL 'QRCVDTAQ' C PARM STJOB C PARM DQLIB C PARM 7 LEN C PARM DQDATA C PARM -1 WAIT 50 C*===================================================== C SETOF 89 C DQRQST IFEQ '*UPDT' C WRITEKEYS1 C GOTO UPDSTS C ENDIF C READ KEYS1 99 C*===================================================== *. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 
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: