Fri, Dec
0 New Articles

TechTip: Changing Triggers on a Busy System

  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times
When your shop runs 24/7 and you have very little scheduled downtime, changing trigger programs can be very hard to do. If you implement triggers in the normal fashion, when a change needs to be done, you are forced to either wait for scheduled downtime or kick everyone off the system. This is because, in order to compile the trigger program, you must have an exclusive lock on the object that the trigger program is attached to.

The technique I have come up with gets around that problem by using two programs for the trigger, instead of one. This works because you can recompile a called program at any time, and the program that is calling it does not care. The two files to create are a driver program that is specified on the Add Physical File Trigger (ADDPFTRG) command and a workhorse program that the driver calls.

The following example is based upon the trigger example from IBM's Information Center.

I have included only the source for the database file that has the trigger attached to it, which is ATMTRANS. Also, my trigger examples do not show any processing, just how to code the two programs.

The file layout for ATMTRANS is shown in Figure 1:

  A          R ATMTRANR
  A            ATMID          5A         COLHDG('ATM' 'MACHINE' 'ID')
  A            ACCTID         5A         COLHDG('ACCT' 'NUM.')
  A            TCODE          1A         COLHDG('TRANS' 'CODE')
  A            AMOUNT         5S 0       COLHDG('AMT. DEP.' 'WITHDRAWN')
  A          K ATMID

Figure 1: ATMTRANS is the source for the database file that has the trigger attached to it.

The driver program TDRVATM is shown in Figure 2:

   * This is the DRIVER program for a database trigger.  This is the program
   * added by the ADDPFTRG command.  This program will never need to be modified
   * unless the database file is modified.
   * The purpose is only to receive the old record and new record, and call
   * the WORKHORSE program to do the actual processing.
  Dparm1            ds
  DPARM2            DS
   * The parameters come into the program
  C     *ENTRY        PLIST
  C                   PARM                    PARM1
  C                   PARM                    PARM2
   * Call the WORKHORSE program to do the actual work
  C                   CALL      'TWRKATM'
  C                   PARM                    PARM1
  C                   PARM                    PARM2
   * OK, done
  C                   EVAL      *INLR = *ON

Figure 2: This is the driver program for a database trigger.

The workhorse program TWRKATM is shown in Figure 3:

 * This is the WORKHORSE program for a database trigger. This is the program
 * that will actually be doing the work. The reason they are separated is that
 *  a called program can be modified and recompiled at any time.
Dparm1            ds
 * Phys. File Name
D FNAME                   1     10
 * Phys. File Library
D LNAME                  11     20
 * Member Name
D MNAME                  21     30
 * Trigger Event
D TEVEN                  31     31
 * Trigger Time
D TTIME                  32     32
 * Commit Lock Level
D CMTLCK                 33     33
 * Reserved
D RSVFILL1               34     36
D CCSID                  37     40B 0
 * Reserved
D RSVFILL2               41     48
 * Offset to Orig Rec
D ORECOFF                49     52B 0
 * Length of Orig Rec
D ORECLEN                53     56B 0
 * Offset to Orig Null
D ORECNULOFF             57     60B 0
 * Length of Orig Null
D ORECNULLEN             61     64B 0
 *Offset to New Rec
D NRECOFF                65     68B 0
 * Length of New Rec
D NRECLEN                69     72B 0
 * Offset to New Null
D NRECNULOFF             73     76B 0
 * Length of New Null
D NRECNULLEN             77     80B 0
 * Reserved
D RSVFILL3               81     96
 * Old Record Image
D OLDREC                 97    112
 * Old Record Null Map
D OLDRECNULL            113    116
 * New Record Image
D NEWREC                117    132
 * New Record Null Map
D NEWRECNULL            133    136
DPARM2            DS
D LENGTH                  1      4B 0
 * Set up a Data Structure to put the Old and New records into.  Use the
 * DDS of the file, since that's the easiest.  Also, use PREFIX to make the
 * Old and New record fields unique.
DOLDRECDS       E DS                  EXTNAME(ATMTRANS)
D                                     PREFIX(O_)
DNEWRECDS       E DS                  EXTNAME(ATMTRANS)
D                                     PREFIX(N_)
 * The parameters come into the program
C     *ENTRY        PLIST
C                   PARM                    PARM1
C                   PARM                    PARM2
 * Move the new record into the data structure
C                   MOVE      OLDREC        OLDRECDS
C                   MOVE      NEWREC        NEWRECDS
C                   SELECT
C                   WHEN      TEVEN = '1'
C                   EXSR      @INSERT
C                   WHEN      TEVEN = '2'
C                   EXSR      @DELETE
C                   WHEN      TEVEN = '3'
C                   EXSR      @UPDATE
C                   ENDSL
C                   EVAL      *INLR = *ON
 * Routine to be used when a record is inserted into the file
C     @INSERT       BEGSR
C                   ENDSR
 * Routine to be used when a record is deleted from the file
C     @DELETE       BEGSR
C                   ENDSR
 * Routine to be used when a record is updated in the file
C     @UPDATE       BEGSR
C                   ENDSR

Figure 3: This is the workhorse program for a database trigger.

With this technique, whenever you need to change or even disable the trigger events, you only have to modify the workhorse program and re-compile. The only time the driver program would need to be modified is when the layout for the database file changes--which, if you were using the traditional trigger approach, would have to be done anyway.

Note: This example uses hard-coded buffers; for a soft-coded example,
please go to www.ibm.com/redbooks. The Redbook SG256403 contains an example on pages 345-350 for RPG.

--Tim Grove
Robert Weed Plywood Corp.
This email address is being protected from spambots. You need JavaScript enabled to view it.

Did this tip "trigger" a tip idea of your own?

Send your useful tips, tricks, or techniques to

This email address is being protected from spambots. You need JavaScript enabled to view it.



Support MC Press Online

$0.00 Raised:

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: