04
Mon, Nov
1 New Articles

Going 5250 on the Information Superhighway

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

So you want to take your business for a ride on the information superhighway? Do you know where the right on-ramp is? Do you know what the best route is? I’m sorry to say this, my friends, but you will need more than MapQuest.com to help you chart your course for this journey. You will need to determine which technology, which development approach, and which deployment method are best suited to your business needs and to your company’s budget.

Some will “throw the baby out with the bath water” by totally scrapping their AS/400s for an off-the-shelf, (allegedly) Windows NT-based solution. They’ll purchase one without accurately factoring in the long-term costs required to support it, knowing it will not be as robust as their legacy midrange system. (Try calculating your company’s aggregated productivity losses attributable to rebooting your network servers versus IPLing your AS/400.)

Others will think, “What about our legacy green-screen applications? Don’t our users like them?” Speaking of users, what about human nature? You know your users will resist learning a totally new system, and can you even justify the expense of a new off-the- shelf system? Have you considered the effort involved in configuring and deploying a new system? Can you retrofit into your new system all the modifications you have made to your legacy system over the years?

Don’t Worry, Be Happy

As it turns out, you can “Webify” your legacy green-screen applications, while preserving your existing business logic, with a minimum of code intrusion. Here is a case study of how I accomplished just such a task on a client project where I was technical leader of the AS/400 group.

First, the project was divided into two teams. The RPG team made the code insertions on the AS/400 applications. The Visual Basic (VB) team developed the new desktop GUI front-end and interfaced it with the AS/400 through a system-to-system messaging product called Cold Fusion. (The techniques we used will work just as well with other messaging products.)

Second, the technical approach was decided. The client identified the applications to be Web-enabled, choosing a few menus to allow field personnel to access its already


familiar order entry system better. The client decided to use Client Access for PC-to- AS/400 connectivity.

These new Web jobs would initiate and run in batch, using the programs originally written for interactive environments. Each affected program would identify the jobs to determine their origin, with native jobs resulting in normal screen I/O operations. Web jobs, on the other hand, would have to send and receive the same screen information through a set of data queues. All display files involved would be mapped to new data structures to facilitate the passing of data between systems via Cold Fusion.

It was agreed that the VB front-end would do none of its own business logic processing; it would only populate the PC screens. (One exception was table look-ups. Many of the AS/400 tables, such as customer number, were loaded onto the client machine.) All other processing would take place on the AS/400, using already developed, tried-and-true business logic.

Finally, we deployed the solution. As I mentioned, this required no change to existing business logic in the RPG programs. The client’s like-functioning programs were very standardized in that they came from the same templates with the same subroutine names and structures. Consequently, it was easy to insert our standardized subroutines into all of the programs, using a cookie-cutter approach but with surgical precision.

The Nuts and Bolts

Every Web job would first put a record containing job and user information into a single data queue. This queue would be under constant surveillance by a never-ending program on the AS/400 that, upon receipt of a valid queue entry, would create a pair of data queues for the Web job: one for inbound data transfers and another for outbound data transfers. Since the local data area (LDA) wouldn’t be used in these particular applications, we decided to use it to identify Web jobs by placing a code in it.

In their initialization routines, these programs would first determine the job’s origin by looking at the LDA for this code. Because these Web jobs would be running in batch, because batch jobs can’t open display files, and because these display file fields would be used throughout the programs, we had to initialize all such numeric fields upon opening the program, to protect against decimal data errors at execution. As shown in Figure 1 (page
101), we set up some of our constants concerning data queue parameters in the same initialization routine. We then let the program and all its existing logic take over as if nothing had changed.

At the point where the program would normally display a file format, the added identifying logic would either perform normal screen I/O operations (if the job were running natively) or send/receive a screen’s worth of data through the pair of data queues (if the job were being executed from the Web). As shown in Figure 2 (page 101), in preparation for the latter case, each screen field being used throughout the program would have to be moved into the data queue. For each screen format, two additional subroutines were appended to the program: one to move fields from the program and display file to the data queue and another to move data from the data queue to the program fields. Each of these subroutines would then call the Send to Data Queue (QSNDDTAQ) and Receive from Data Queue (QRCVDTAQ) APIs.

We also built program termination controls into the program so that, if communications were disrupted, the job wouldn’t just “hang” there, looking at a data queue for a response that would never appear. We set a timeout threshold of 60 minutes, after which time the program would exit gracefully.

For testing, we had to build some of our own tools. The RPG team did not always work in concert with the VB team, so we created a screen that acted as a client in that it would read the outbound data queue and write to the inbound data queue. This allowed the RPG team to see exactly what we were sending to the VB side without the VB programs even being written for any particular function.


Always Room for Improvement

In retrospect, there are some lessons to learn from this project. First and probably foremost, the RPG and VB teams should have been closer to each other. (We were in different regional offices.) That would have greatly enhanced our development and testing efforts. Second, Cold Fusion may not have been as effective as MQSeries might have been. (See “Get the Message with MQSeries” elsewhere in this issue.) As it turns out, the response time could have been greatly reduced.

.

. (pre-existing business logic)
.

* Retrieve *LDA (in init routine)
C *DTAARA Define *LDA LDA
C In LDA

*

C If (SourceSys 'W')
C Open DSPFILE
C Else
C MoveL '*LIBL' DQLib
C Z-Add 3600 DQTimeOut
.

. (any other data queue and/or web specific initialization)
.

C EndIf
.

. (more pre-existing business logic)
.

* Move screen data to data queue and send the data queue
C SndSFLctl BegSR
C Move *Blanks DQData

* Move screen/pgm fields to data queue
C Move SFLRRN SFRRN2
C Move OrdNum OrdNu2
C MoveL Fmt2 DQData
C MoveL DtaQout DQName
C Call 'QSNDDTAQ'
C Parm DQName
C Parm DQLib
C Parm DQLength
C Parm DQData
.

. (more pre-existing business logic)
.

C RcvSFLctl BEGSR
C Move *Blanks DQData
C MoveL DtaQin DQName
C Call 'QRCVDTAQ'
C Parm DQName
C Parm DQLib
C Parm DQLength
C Parm DQData
C Parm DQTimeOut

* Move data queue fields to screen/pgm
C MoveL SFRRN2 SFLRRN
C MoveL OrdNu2 OrdNum

* *DTAQ timed-out
C If (DQData = *Blank)
. (Handle your data queue timeout action)
C EndIf
.

. (more pre-existing business logic)
.

Figure 1: Business logic is not affected by changes, allowing the program to run either natively or from a GUI client.

* Sample of screen I/O conditioning logic

*

* SFLctl -- format name of the SFL control record for

* native displays

* SndSFLCtl and RcvSFLCtl -- the subroutines to move

* screen/program data into the send data queue output


* parameter and to move the receive data queue input

* into the screen/program fields, respectively, and

* calls the appropriate SND/RCVDTQ API.
.

. (pre-existing business logic)
.

C If SourceSys = 'W'
C Exsr SndSFLCtl
C Exsr RcvSFLCtl
C Else
C Write SFLctl
C Read SFLctl
C EndIf
.

. (pre-existing business logic)
.

To load the subfile was very simple. SndSFL moves screen/program data into the send data queue output and
calls the SNDDTQ API.

.

. (pre-existing business logic)
.

C If SourceSys = 'W'
C Exsr SndSFL
C Else
C Write SFLrcd
C EndIf
.

. (pre-existing business logic)
.

Figure 2: I/O routines are modified to use either subfiles or data queues.


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: