Are You Taking Full Advantage of the System Entry Point Table Object?

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

Achieve API invocation performance gains and discover a new pointer caching technique.


The System Entry Point Table (SEPT) object, QSYS/QINSEPT, is a space object with MI object type/subtype code hex 19C3 and external object type *SEPT. It is designed to improve the performance of invocation of program objects in library QSYS. The SEPT stores authorized system pointers to many (but not all) of the user domain/system state (aka API) or system domain/system state program objects residing in library QSYS in its associated space.


User programs are always of user domain and run under user state. The user domain/system state APIs are the glue between user programs and their system domain/system state counterparts. Since they are of user domain, they can be called by user code. And since they run under system state, they can call system domain programs. For example, each time you request to open a database file object, the user domain/system state API QDMCOPEN is called, and QDMCOPEN then calls the system domain/system state program QDBOPEN to achieve the actual operation on the target database file. Protections such as parameter validation are performed by user domain/system state APIs before controls are passed to system domain/system programs.


The SEPT is addressable to each MI process (an i5/OS job) through the Process Control Space (PCS) object. A PCS is an MI object (with object type/subtype code hex 1AEF) used by i5/OS to control the execution of an MI process. The PCS is also referred to as the job structure. An MI process can be uniquely identified by a PCS object. A PCS object contains work areas and storage needed by an MI process, such as process storage spaces for stack, static, and heap storage. The associated space of a PCS object contains the Process Communication Object (PCO). When a PCS object is created and allocated to an MI process, a space pointer addressing the associated space of the SEPT is stored at the beginning of the PCO.


So how does the SEPT improve the performance of invocation of program objects in library QSYS?


Entries (system pointers) in the SEPT are resolved in the installation stage of the system. The number of SEPT entries and the position of a system pointer to a particular program object is the same for each installation for a specific i5/OS release. Newly introduced APIs are appended at the end of the SEPT. For example, the number of entries in the SEPT is 6700 and 7001, respectively, at V5R2 and V5R4. By calling a program in library QSYS via the system pointer to it stored in the SEPT, user programs can spare the time being consumed in locating the target program object by using MI instruction Resolve System Pointer (RSLVSP) to resolve a system pointer to the program object via the symbolic identification (object and optional library name).


So is it really so time-consuming to resolve a system pointer to an MI object? Let's find out.


The following two ILE RPG programs, jan23b.rpgle and jan25b.rpgle, call the Send Data Queue (QSNDDTAQ) API to enqueue a queue entry to a data queue object. The only difference between them is that jan23b.rpgle calls QSNDDATQ directly using the ILE PRG operation code CALL and passing the name of the API, while jan25b.rpgle calls QSNDDTAQ via a resolved system pointer in the SEPT.


This is the source code of ILE RPG program jan23b.rpgle.


     d e               s             16a


     c                   time                    w                14 0

     c                   movel     w             e

     c                   call      'QSNDDTAQ'

     c                   parm      'JAN23'       qname            10

     c                   parm      'LSBIN'       qlib             10

     c                   parm      16            elen              5 0

     c                   parm                    e


     c                   seton                                          lr


Here is the source code of ILE RPG program jan25b.rpgle.


     h dftactgrp(*no)

     /* Prototype of PCOPTR2 */

     d pcoptr2         pr              *   extproc('_PCOPTR2')

     /* Prototype of CALLPGMV */

     d callpgmv        pr                  extproc('_CALLPGMV')

     d     pgm_ptr                     *

     d     argv                        *   dim(1) options(*varsize)

     d     argc                      10u 0 value


     d pco_ptr         s               *

     d pco             ds                  qualified

     d                                     based(pco_ptr)

     d     sept_ptr                    *


     d septs           s               *   dim(7001)

     d                                     based(pco.sept_ptr)


     d qsnddtaq        s               *

     d argv            s               *   dim(4)

     d qname           s             10a   inz('JAN23')

     d qlib            s             10a   inz('LSBIN')

     d qent            s             16a

     d len             s              5p 0 inz(16)




           pco_ptr = pcoptr2();

           qsnddtaq = septs(2898);


           qent = %char(%time : *iso);

           argv(1) = %addr(qname);

           argv(2) = %addr(qlib);

           argv(3) = %addr(len);

           argv(4) = %addr(qent);

           callpgmv(qsnddtaq : argv : 4);


           *inlr = *on;



If you call these two programs 100,000 times on a V5R4 machine, you might get the following results: jan23b takes 9.198 seconds, and jan25b takes 2.306 seconds. Clearly, resolving a system pointer to a program object (the QSNDDTAQ API) might be much more time-consuming than the actual work done by the called program.


In the example ILE RPG program jan25b.rpgle, MI instruction Return PCO Pointer (PCOPTR2) is used to obtain addressability of the PCO of the current MI process in the form of a space pointer. As mentioned above, a space pointer to the SEPT is at the beginning of the PCO, so when the address of space pointer pco_ptr is returned upon a successful completion of _PCOPTR2, the array elements in the system pointer array septs are available. Finally, jan25b.rpgle calls the QSNDDTAQ API via the resolved system pointer to program object QSNDDTAQ, whose index number in the SEPT is hex 0B51 (start from zero). MI instruction Call Program with Variable Length Argument List (CALLPGMV) is used to call program object QSNDDTAQ via the resolved system pointer to it.


To avoid hard-coding the index numbers of SEPT entries, you might dump the SEPT of your target i5/OS release and convert the offset values of system pointers in it to a list of declarations of constants. To dump the SEPT, you can dump space object QSYS/QINSEPT either directly or via the space pointer to the SEPT that is at the beginning of the PCO of an MI process. Here are the example CL commands.


/* Dump the SEPT object directly */



/* Dump the SEPT via the PCO object */



The following declaration of the index number in SEPT of the User Interface Manager (UIM) API Display Long Text (QUILNGTX) is extracted from ept54.rpgleinc, which is provided by the open-source project i5/OS Programmer's Toolkit.


     /* Display Long Text (QUILNGTX) API */

     d ept_quilngtx    c                   x'1629'


The following ILE RPG program, t064.rpgle, calls QUILNGTX by using the index number of QUILNGTX's entry in the SEPT.


     h dftactgrp(*no)


      /copy mih54

      /copy ept54


     d pco_ptr         s               *

     d pco             ds                  qualified

     d                                     based(pco_ptr)

     d     sept_ptr                    *

     d septs           s               *   dim(7001)

     d                                     based(pco.sept_ptr)


     d argv            s               *   dim(5)

     /* arguments of QUILNGTX */

     d text            s              8a   inz('The SEPT')

     d len             s             10i 0 inz(8)

     d msgid           s              7a   inz('CPF9898')

     d msgf            s             20a   inz('QCPFMSG   QSYS')

     d ec              s             16a



           pco_ptr = pcoptr2();


           ec = x'00000010000000000000000000000000';

           argv(1) = %addr(text);

           argv(2) = %addr(len);

           argv(3) = %addr(msgid);

           argv(4) = %addr(msgf);

           argv(5) = %addr(ec);

      /if defined(*v5r4m0)

           callpgmv( septs(ept_quilngtx) // hex 162A

                   : argv : 5);



           *inlr = *on;



There is yet another method to obtain the addressability of the SEPT. The undocumented system built-in _SYSEPT can be found in ILE C/C++ header QSYSINC/MIH(SYSEPT). _SYSEPT returns a space pointer to the SEPT. The following is the ILE RPG prototype of _SYSEPT extracted from mih52.rpgleinc.


     /* returns a space pointer to the SEPT */

     d sysept          pr              *   extproc('_SYSEPT')


In the following ILE RPG program t065.rpgle, _SYSEPT is used to obtain the addressability of the SEPT.


     h dftactgrp(*no)


      /copy mih54

      /copy ept54


     d ept_ptr         s               *

     d septs           s               *   dim(7001)

     d                                     based(ept_ptr)

     d argv            s               *   dim(1)



           // address the SEPT

           ept_ptr = sysept();


      /if defined(*v5r4m0)

           // call Operational Assistant API Send Message (QEZSNDMG)

           callpgmv( septs(EPT_QEZSNDMG)

                   : argv

                   : 0);



           *inlr = *on;



SEPT's value is not only the performance gains in API invocation; the design of the SEPT also introduces a pointer caching technique to us. The virtual address stored in the system pointer to an MI object is a single-level storage (SLS) address in the 64-bit virtual address space of i5/OS. And this virtual address remains unchanged during the life of an MI object. This means that system pointers to permanent MI objects stored in a permanent MI object (such as a permanent space object, a permanent index object, or a queue object that can contain pointers) will remain valid and can be reused even across IPLs.


Junlei Li

Junlei Li is a programmer from Tianjin, China, with 10 years of experience in software design and programming. Junlei Li began programming under i5/OS (formerly known as AS/400, iSeries) in late 2005. He is familiar with most programming languages available on i5/OS—from special-purpose languages such as OPM/ILE RPG to CL to general-purpose languages such as C, C++, Java; from strong-typed languages to script languages such as QShell and REXX. One of his favorite programming languages on i5/OS is machine interface (MI) instructions, through which one can discover some of the internal behaviors of i5/OS and some of the highlights of i5/OS in terms of operating system design.


Junlei Li's Web site is, where his open-source project i5/OS Programmer's Toolkit ( is documented.



Support MC Press Online





  • White Paper: Node.js for Enterprise IBM i Modernization

    SB Profound WP 5539

    If your business is thinking about modernizing your legacy IBM i (also known as AS/400 or iSeries) applications, you will want to read this white paper first!

    Download this paper and learn how Node.js can ensure that you:
    - Modernize on-time and budget - no more lengthy, costly, disruptive app rewrites!
    - Retain your IBM i systems of record
    - Find and hire new development talent
    - Integrate new Node.js applications with your existing RPG, Java, .Net, and PHP apps
    - Extend your IBM i capabilties to include Watson API, Cloud, and Internet of Things

    Read Node.js for Enterprise IBM i Modernization Now!


  • Profound Logic Solution Guide

    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 companyare not aligned with the current IT environment.

    Get your copy of this important guide today!


  • 2022 IBM i Marketplace Survey Results

    Fortra2022 marks the eighth edition of the IBM i Marketplace Survey Results. Each year, Fortra captures data on how businesses use the IBM i platform and the IT and cybersecurity initiatives it supports.

    Over the years, this survey has become a true industry benchmark, revealing to readers the trends that are shaping and driving the market and providing insight into what the future may bring for this technology.

  • Brunswick bowls a perfect 300 with LANSA!

    FortraBrunswick is the leader in bowling products, services, and industry expertise for the development and renovation of new and existing bowling centers and mixed-use recreation facilities across the entertainment industry. However, the lifeblood of Brunswick’s capital equipment business was running on a 15-year-old software application written in Visual Basic 6 (VB6) with a SQL Server back-end. The application was at the end of its life and needed to be replaced.
    With the help of Visual LANSA, they found an easy-to-use, long-term platform that enabled their team to collaborate, innovate, and integrate with existing systems and databases within a single platform.
    Read the case study to learn how they achieved success and increased the speed of development by 30% with Visual LANSA.


  • The Power of Coding in a Low-Code Solution

    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:

    • Discover the benefits of Low-code's quick application creation
    • Understand the differences in model-based and language-based Low-Code platforms
    • Explore the strengths of LANSA's Low-Code Solution to Low-Code’s biggest drawbacks



  • Why Migrate When You Can Modernize?

    LANSABusiness 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.
    In this white paper, you’ll learn how to think of these issues as opportunities rather than problems. We’ll explore motivations to migrate or modernize, their risks and considerations you should be aware of before embarking on a (migration or modernization) project.
    Lastly, we’ll discuss how modernizing IBM i applications with optimized business workflows, integration with other technologies and new mobile and web user interfaces will enable IT – and the business – to experience time-added value and much more.


  • UPDATED: Developer Kit: Making a Business Case for Modernization and Beyond

    Profound Logic Software, Inc.Having trouble getting management approval for modernization projects? The problem may be you're not speaking enough "business" to them.

    This Developer Kit provides you study-backed data and a ready-to-use business case template to help get your very next development project approved!

  • What to Do When Your AS/400 Talent Retires

    FortraIT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators is small.

    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:

    • Why IBM i skills depletion is a top concern
    • How leading organizations are coping
    • Where automation will make the biggest impact


  • Node.js on IBM i Webinar Series Pt. 2: Setting Up Your Development Tools

    Profound Logic Software, Inc.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. In Part 2, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Attend this webinar to learn:

    • Different tools to develop Node.js applications on IBM i
    • Debugging Node.js
    • The basics of Git and tools to help those new to it
    • Using as a pre-built development environment



  • Expert Tips for IBM i Security: Beyond the Basics

    SB PowerTech WC GenericIn this session, IBM i security expert Robin Tatam provides a quick recap of IBM i security basics and guides you through some advanced cybersecurity techniques that can help you take data protection to the next level. Robin will cover:

    • Reducing the risk posed by special authorities
    • Establishing object-level security
    • Overseeing user actions and data access

    Don't miss this chance to take your knowledge of IBM i security beyond the basics.



  • 5 IBM i Security Quick Wins

    SB PowerTech WC GenericIn today’s threat landscape, upper management is laser-focused on cybersecurity. You need to make progress in securing your systems—and make it fast.
    There’s no shortage of actions you could take, but what tactics will actually deliver the results you need? And how can you find a security strategy that fits your budget and time constraints?
    Join top IBM i security expert Robin Tatam as he outlines the five fastest and most impactful changes you can make to strengthen IBM i security this year.
    Your system didn’t become unsecure overnight and you won’t be able to turn it around overnight either. But quick wins are possible with IBM i security, and Robin Tatam will show you how to achieve them.

  • Security Bulletin: Malware Infection Discovered on IBM i Server!

    SB PowerTech WC GenericMalicious programs can bring entire businesses to their knees—and IBM i shops are not immune. It’s critical to grasp the true impact malware can have on IBM i and the network that connects to it. Attend this webinar to gain a thorough understanding of the relationships between:

    • Viruses, native objects, and the integrated file system (IFS)
    • Power Systems and Windows-based viruses and malware
    • PC-based anti-virus scanning versus native IBM i scanning

    There are a number of ways you can minimize your exposure to viruses. IBM i security expert Sandi Moore explains the facts, including how to ensure you're fully protected and compliant with regulations such as PCI.



  • Encryption on IBM i Simplified

    SB PowerTech WC GenericDB2 Field Procedures (FieldProcs) were introduced in IBM i 7.1 and have greatly simplified encryption, often without requiring any application changes. Now you can quickly encrypt sensitive data on the IBM i including PII, PCI, PHI data in your physical files and tables.
    Watch this webinar to learn how you can quickly implement encryption on the IBM i. During the webinar, security expert Robin Tatam will show you how to:

    • Use Field Procedures to automate encryption and decryption
    • Restrict and mask field level access by user or group
    • Meet compliance requirements with effective key management and audit trails


  • Lessons Learned from IBM i Cyber Attacks

    SB PowerTech WC GenericDespite the many options IBM has provided to protect your systems and data, many organizations still struggle to apply appropriate security controls.
    In this webinar, you'll get insight into how the criminals accessed these systems, the fallout from these attacks, and how the incidents could have been avoided by following security best practices.

    • Learn which security gaps cyber criminals love most
    • Find out how other IBM i organizations have fallen victim
    • Get the details on policies and processes you can implement to protect your organization, even when staff works from home

    You will learn the steps you can take to avoid the mistakes made in these examples, as well as other inadequate and misconfigured settings that put businesses at risk.



  • The Power of Coding in a Low-Code Solution

    SB PowerTech WC GenericWhen 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:

    • Discover the benefits of Low-code's quick application creation
    • Understand the differences in model-based and language-based Low-Code platforms
    • Explore the strengths of LANSA's Low-Code Solution to Low-Code’s biggest drawbacks



  • Node Webinar Series Pt. 1: The World of Node.js on IBM i

    SB Profound WC GenericHave 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.
    Part 1 will teach you what Node.js is, why it's a great option for IBM i shops, and how to take advantage of the ecosystem surrounding Node.
    In addition to background information, our Director of Product Development Scott Klement will demonstrate applications that take advantage of the Node Package Manager (npm).
    Watch Now.

  • The Biggest Mistakes in IBM i Security

    SB Profound WC Generic The Biggest Mistakes in IBM i Security
    Here’s the harsh reality: cybersecurity pros have to get their jobs right every single day, while an attacker only has to succeed once to do incredible damage.
    Whether that’s thousands of exposed records, millions of dollars in fines and legal fees, or diminished share value, it’s easy to judge organizations that fall victim. IBM i enjoys an enviable reputation for security, but no system is impervious to mistakes.
    Join this webinar to learn about the biggest errors made when securing a Power Systems server.
    This knowledge is critical for ensuring integrity of your application data and preventing you from becoming the next Equifax. It’s also essential for complying with all formal regulations, including SOX, PCI, GDPR, and HIPAA
    Watch Now.

  • Comply in 5! Well, actually UNDER 5 minutes!!

    SB CYBRA PPL 5382

    TRY 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.

    Request your trial now!

  • Backup and Recovery on IBM i: Your Strategy for the Unexpected

    FortraRobot automates the routine 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:
    - Simplified backup procedures
    - Easy data encryption
    - Save media management
    - Guided restoration
    - Seamless product integration
    Make sure your data survives when catastrophe hits. Try the Robot Backup and Recovery Solution FREE for 30 days.

  • Manage IBM i Messages by Exception with Robot

    SB HelpSystems SC 5413Managing messages on your IBM i can be more than a full-time job if you have to do it manually. 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:
    - Automated message management
    - Tailored notifications and automatic escalation
    - System-wide control of your IBM i partitions
    - Two-way system notifications from your mobile device
    - Seamless product integration
    Try the Robot Message Management Solution FREE for 30 days.

  • Easiest Way to Save Money? Stop Printing IBM i Reports

    FortraRobot 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:

    - Automated report distribution
    - View online without delay
    - Browser interface to make notes
    - Custom retention capabilities
    - Seamless product integration
    Rerun another report? Never again. Try the Robot Report Management Solution FREE for 30 days.

  • Hassle-Free IBM i Operations around the Clock

    SB HelpSystems SC 5413For over 30 years, Robot has been a leader in systems management for IBM i.
    Manage your job schedule with the Robot Job Scheduling Solution. Key features include:
    - Automated batch, interactive, and cross-platform scheduling
    - Event-driven dependency processing
    - Centralized monitoring and reporting
    - Audit log and ready-to-use reports
    - Seamless product integration
    Scale your software, not your staff. Try the Robot Job Scheduling Solution FREE for 30 days.