24
Sun, Nov
1 New Articles

TechTalk: Combining Files Through a Logical View

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

Q: Could someone please enlighten me on the best way to combine data from two files, perform record selection and resequence the file for use by RPG/400?

My situation is this: I have two externally described physical files on my system, an order header file (containing current orders) and a past sales file (containing invoiced orders). Each file has a unique record format name, but identical file layouts and field names. I need to combine all records from both files to be used by an RPG/400 program as an IP file for a monthly report. Bear in mind that the order header file has 10,000 records and the past sales file can have as many as 600,000 records.

I first tried building a multiple-format logical file that contained the two files and then used OPNQRYF for record selection and resequencing. Result: OPNQRYF bombed out due to multiple record formats in the logical file. Then I tried joining the two files using OPNQRYF and it bombed again! This error message indicated that I couldn't have the same field names in both files. From reading the manuals (a lot of manuals!), a joined-logical file using DDS is out of the question since I need every record and field from both files.

After pulling out most of my hair in clumps, I have finally reverted to this: building an empty physical file as a work file, using CPYF (twice) to combine the two files into the work file and then using a standard OPNQRYF against the work file for record selection and resequencing. The program now runs fine, but it is obviously very slow in the file build and record selection departments, as well as gobbling up much needed resources.

There must be a better way?!

A: There is! You were on the right track with your first approach, building a multiple-format logical file. The problem was that instead of defining a separate record format for each of the physical files, what needs to be done is to define one record format and specify both of the physical files on that format.

For example, if two physical files, PHYFIL01 and PHYFIL02, as shown in1a and 1b, needed to be combined into one logical file you would use the DDS shown in 1c. The names to the physical files (up to 32) are specified using the PFILE keyword. If all of the fields of one of the physical files are to be included, use that format name in the logical file. DDS will find all of the fields that the format you specify--in this case FORMAT1--has in common with the other files you specified on the PFILE keyword. It takes this information and creates a format that contains all of the fields that are common to all of the files. In other words, a field must be in each and every one of the files to be included in this format. A key field must also be specified, in this case FIELD1, since DDS requires that if more than one file is specified on the PFILE keyword, a key must be specified. If, on the other hand, you wanted to include only selected fields from the physical files, you could use the DDS shown in 1d.

For example, if two physical files, PHYFIL01 and PHYFIL02, as shown in Figures 1a and 1b, needed to be combined into one logical file you would use the DDS shown in Figure 1c. The names to the physical files (up to 32) are specified using the PFILE keyword. If all of the fields of one of the physical files are to be included, use that format name in the logical file. DDS will find all of the fields that the format you specify--in this case FORMAT1--has in common with the other files you specified on the PFILE keyword. It takes this information and creates a format that contains all of the fields that are common to all of the files. In other words, a field must be in each and every one of the files to be included in this format. A key field must also be specified, in this case FIELD1, since DDS requires that if more than one file is specified on the PFILE keyword, a key must be specified. If, on the other hand, you wanted to include only selected fields from the physical files, you could use the DDS shown in Figure 1d.

The logical file that is created can be used in the same way as any other logical file, including being processed by OPNQRYF. There is one restriction, however: the logical file can't be used to provide an external file definition for RPG/400. The reason for this is that the logical file created is actually a multiple-format logical file, but all of the formats have the same name. This doesn't seem to bother OPNQRYF, but since RPG/400 doesn't allow duplicate format names, a problem arises. Normally you would just RENAME the format in the F spec, but in this case you can't because RPG/400 wouldn't know which of the formats to rename. The easiest solution is, if you are using the format of an existing file as we did is 1c (page 63), use the name of that physical file in your RPG program and then use an OVRDBF when you run the program. Another way would be to create a temporary physical file that contains all the information that RPG/400 needs, and then after the program is compiled, delete it.

The logical file that is created can be used in the same way as any other logical file, including being processed by OPNQRYF. There is one restriction, however: the logical file can't be used to provide an external file definition for RPG/400. The reason for this is that the logical file created is actually a multiple-format logical file, but all of the formats have the same name. This doesn't seem to bother OPNQRYF, but since RPG/400 doesn't allow duplicate format names, a problem arises. Normally you would just RENAME the format in the F spec, but in this case you can't because RPG/400 wouldn't know which of the formats to rename. The easiest solution is, if you are using the format of an existing file as we did is Figure 1c (page 63), use the name of that physical file in your RPG program and then use an OVRDBF when you run the program. Another way would be to create a temporary physical file that contains all the information that RPG/400 needs, and then after the program is compiled, delete it.


TechTalk: Combining Files Through a Logical View

Figure 1A DDS for PHYFIL01

 Figure 1a: DDS for PHYFIL01 A R FORMAT1 A FIELD1 5P 0 A FIELD2 25A A FIELD3 10A A K FIELD1 
TechTalk: Combining Files Through a Logical View

Figure 1B DDS for PHYFIL02

 Figure 1b: DDS for PHYFIL02 A R FORMAT2 A FIELD1 5P 0 A FIELD2 25A A FIELD3 10A A K FIELD1 
TechTalk: Combining Files Through a Logical View

Figure 1C DDS for including all records from two PFs

 Figure 1c: DDS for Including All Records From Two Physical Files A R FORMAT1 PFILE(PHYFIL01 PHYFIL02) A K FIELD1 
TechTalk: Combining Files Through a Logical View

Figure 1D DDS for including only selected fields

 Figure 1d: DDS for Including Only Selected Fields A R FORMAT3 PFILE(PHYFIL01 PHYFIL02) A FIELD1 A FIELD2 A K FIELD2 
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: