29
Fri, Nov
0 New Articles

Getting Your Ducks in a Row

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

If you’ve ever done any work in database design, you’re familiar with the concept of using “codes” to represent various forms of data. Codes take up less space on disk, a fact especially important to those of us designing systems anytime prior to the last few years. Online and offline storage used to be really expensive, and we had to design fully functional systems while using the least amount of DASD (disk) possible. (This is how the six-digit date came about, but that is a topic best reserved for another story.)

Quacks in the Armor

Using codes in your database has its problems, however. The most obvious problem is that you create a situation that requires extra I/O processing whenever you need to translate codes into text. It’s a trade-off between how much storage space you use on disk and working the disk access arms off until they’re nubs.

Another problem with codes is that they aren’t always entirely useful when you want to sequence data for reporting purposes. For example, suppose a transaction file contains charges, payments, and adjustments all stored in a single data file, and a transaction type code differentiates each type of transaction. (For this example, we’re using type codes C for charge, P for payment, and A for adjustment.) And as long as we are making suppositions, let’s say the transaction file happens to be the largest file on the system and contains 10 million records. Now, suppose a client calls up and requests a transaction report that usually prints in adjustment/charge/payment order be changed so that it prints in charge/adjustment/payment order. This seems like a simple enough change, but, upon further review, you realize that this may be a bigger job than you thought. The report prints in the order it does because the codes for adjustments, charges, and payments are A, C, and P, respectively. If the client asks you to report the transactions in payment/charge/adjustment order, you would simply process the transactions in descending order by transaction type code. However, because this isn’t the case, your only options seem to be to create a work file keyed in the desired sequence, to use multiple logical files over each type of record, or to change the program to make multiple passes through the data file. Each option involves a dramatic increase in processing time, a luxury you can’t afford, so how do you accomplish this task?

Ducking for Cover

A more logical approach is to use a table file to create an alternate collating sequence that allows the system to read the transaction file in the desired sequence in a single pass through the data. To do this in the example, you would position code C before code A so the report could print the transactions in charge/adjustment/payment order.

Rubber Ducky, You’re the One!

The Create Table (CRTTBL) command enables you to create a table that both logical files and the Open Query File (OPNQRYF) command can use to alter the normal character sequence. To create a table like the table in Figure 1, key in the following command:

CRTTBL TBL(QGPL/TRANSORT)SRCFILE(*PROMPT)TBLTYPE(*SRTSEQ)

The Table type (TBLTYPE) parameter accepts three codes: *CVT, which creates a conversion table; *SRTSEQ, which creates a sort sequence table; and *UCSSRTSEQ, which creates a Unicode sort sequence table. *CVT changes a character from one hexadecimal value to another; *SRTSEQ simply alters the sequence in which characters are processed. *SRTSEQ and *UCSSRTSEQ use different standards to create sort sequence tables, but we use only *SRTSEQ because *UCSSRTSEQ requires a hexadecimal code point and weight for each character.

The SRCFILE parameter requires the name of a source file member that contains the hexadecimal conversion characters used to create the table. You can specify a source member name, but we find it easier to use the *PROMPT value for the SRCFILE parameter. *PROMPT prompts a screen similar to Figure 1. The numbered sequence column is the order in which the character in the next column is processed. In our example, you want transaction records with type code C (charges) to appear in the file before transaction records with type code A (adjustments). This being the case, you must press the Page keys until you find C, which is sequence number 1310 (see Figure 2). A is sequence number 1290, so it normally appears before C. However, if you change the sequence number of C to 1281 and press Enter, C now appears before A. (Figure 3 shows the results of making this change.) As soon as you’re happy with your sort sequence, press F6 to create the table.

The instructions on the screen tell you to key in the same sequence number to have characters sort in a group. An alternative sort sequence table might be useful when you have mixed-case characters (possibly a name) in a field and want to sort on that field. If you key in the same sequence number for the lowercase “a” and uppercase “A,” for instance, the two characters sort as if they contain the same value.

Figure 4 shows sample DDS from a logical file that uses our table. The table is named TRANSORT and can be found in library QGPL. The ALTSEQ keyword, at the DDS file level, instructs the file to use an alternative sequence stored in TRANSORT. There are two key fields for this logical file, but you want the table applied only to the TRTYPE key field because TRTYPE contains the transaction type code. The NOALTSEQ keyword tells the system not to apply the table to this field.

OPNQRYF can also use a sort sequence table. The SRTSEQ parameter specifies the name of the table to use.

Everything Is Just Ducky!

If you work with large database files, you will find that the fewer times you have to pass through the file, the more efficiently your system processes. “Tricking” the system to read data in an alternate sequence may save you quite a bit of processing. This is just another example of how knowledge is power!

<>
<>
<>

Figure 1: The *PROMPT parameter creates an alternate sort sequence table.


Figure 2: Use the Page keys to find your desired characters.


Figure 3: You can even change the sequence of characters from A-B-C to C-A-B.



Getting_Your_Ducks_in_a_Row03-00.png 595x372
<>
<>
<>

Getting_Your_Ducks_in_a_Row03-01.png 597x368
<>
<>
<>

Getting_Your_Ducks_in_a_Row03-02.png 595x366

A ALTSEQ(QGPL/TRANSORT)

A R TRNREC PFILE(TRANS)

A K TRTYPE

A K TRFAM# NOALTSEQ

Figure 4: This logical file DDS uses an alternate sort sequence table.

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: