13
Wed, Nov
5 New Articles
  1. You are here:  
  2. Home
  3. Programming
  4. RPG
  5. TechTip: System Catalogs

TechTip: System Catalogs

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

A system catalog is essentially a database file that i5/OS maintains behind the scenes and then uses to track objects and other information on the system. And a little bit of basic knowledge about them can make programming simpler for you.

As an example, let's talk about QADBXREF (the Database Cross-Reference system catalog). This system catalog is a physical file with an object of type *FILE and an attribute of PF-DTA. It contains a record for each database file and SQL table on your iSeries. Whenever you add a file to your iSeries—using CRTPF, CRTLF, CREATE TABLE, etc.— i5/OS adds a record to QADBXREF containing all sorts of information about that file: file name, library name, attribute of the file (physical, logical, table, index, view, etc.), owner.... In fact, here's a list of all the fields in QADBXREF:

Field Description
Field Name
 Field Type
Start Position
File name
DBXFIL
10 A
1
Library name
DBXLIB
10 A
11
Dictionary name
DBXDIC
10 A
21
User profile name of owner
DBXOWN
10 A
31
File text
DBXTXT
50 A
41
PF=physical, LF=logical, TB=table
DBXATR
2 A
91
E=ext
DBXLNK
1 A
93
I=IDDU, S=SQL, C=CRTDTADCT, X
DBXSQL
1 A
94
D=data file, S=source file
DBXTYP
1 A
95
Maximum number of fields
DBXNFL
5 S 0
96
Maximum number of key fields
DBXNKF
5 S 0
101
Maximum record length
DBXRDL
11 S 0
106
Dictionary internal file
DBXIDV
11 S 0
117
Relational file: Y=Yes, N=No
DBXREL
1 A
128
Long file name
DBXLFI
130 A
129
Long file name is quoted
DBXLFQ
1 A
259
C=CASCADED, Y=Yes (local),
DBXWCO
1 A
260
Y=Yes, N=No
DBXUPD
1 A
261
D=No, V=Yes (allow NULL)
DBXUNQ
1 A
262
Long file description
DBXREM
 2002 A 263
SQL VIEW definition
DBXDFN
10002 A
2265
File change timestamp
DBXATS
Z
12267
Library name
DBXLB2
130 A
12293
Alias relational database
DBXADB
20 A
12423
Alias library name
DBXALB
130 A
12443
Alias file name
DBXAFL
130 A
12573
Alias member name
DBXAMB
12 A
12703
Y=Yes, N=No
DBXINSERT
1 A
12715
Primary ASP
DBX_PASP
5 I 0
12716
Y=S/O logical, D=DYNSLT, N
DBXSO
1 A
12718
Y=system File
DBXSYS
1 A
12719
Number of partitions
DBXPART
5 I 0
12720
Index over partitioned TBL
DBXISPAN
1 A
12722


So what can system catalogs do for you? They provide an alternative means to solve certain problems. If you have an application that needs a list of files on the system, you can...

  • Get that list using an API. This requires some complex coding, and probably a user space.
  • Use DSPFD to generate a list of files to an output file. This requires a front-end CL driver and possibly some database overriding.
  • Simply read QADBXREF from your program.

System catalogs have logical files, so you can use the access path that best meets your needs. Use DSPDBR and DSPFD to find the best logical. You can also create your own logicals, which many applications do.

SQL creates logical files over system catalogs as well—for example, SYSTABLES. In fact, a SYSTABLES file is generated for every schema created through SQL, selecting only the files in that schema.

Now, some things to be aware of when using system catalogs:

  • Always open them as input, never as update. Access them only as read-only.
  • You may not have enough authority to use a system catalog. If not, try one of its logicals.
  • Study the record format and fields of a system catalog carefully; some information you need may not be immediately available and will need to be calculated.

Other useful system catalogs:

  • QADBIFLD lists every field and column on your iSeries.
  • QADBKFLD lists every key field and column on your iSeries.
  • QADBXTRIGB lists the triggers on your iSeries. I once published a utility called Trigger Tracker that uses this system catalog.
  • QAOKP01A lists the users in the System Distribution Directory.
  • QATMSMTPA contains the email addresses for the users in the System Distribution Directory.

Here is a sample program using QAOKP01A and QATMSMTPA:

 ***************************************************************** 
 *                                                               * 
 * Program   - GETUDEM                                           * 
 *                                                               * 
 * Narrative : Get User's email address from the System          *
 *             Distribution Directory                            *
 *                                                               *
 * Written : Doug Eckersley                                      *
 *           08/21/2003                                          *
 *****************************************************************
 ********------------ Program Maintenance Log ------------********
 *****************************************************************
 * Personnel  |   Date   | Comments/Description                  *
 *------------|----------|---------------------------------------*
 *            |          |                                       *
 *****************************************************************
H dftactgrp(*no) option(*nodebugio) datfmt(*iso)  
                                      
FQAOKL02A  IF   E           K DISK    
FQATMSMTPA IF   E           K DISK  
                                                          
D*==================================================================
D* Parameters                                         
D*==================================================================
D inUser          S             10A                   
D outAddress      S             50A                 
D                                         
D*==================================================================
D* Program Status DS                                 
D*==================================================================
D***/copy DSDS                                    
D #User           S             10A   inz(*user)
D UCase           C                   'ABCDEFGHIJKLMNOPQRSTUVWXYZ' 
D LCase           C                   'abcdefghijklmnopqrstuvwxyz'
D                                                  
                                                
C*******************************************************************
C*******************************************************************
C     *entry        plist                                
C                   parm                    inUser       
C                   parm                    outAddress     
C                                                                   
 /free                                                 
                                                                    
  exsr $inzsr;                                                    
  exsr $Main;                                                     
                                                                
  *inlr = *on;                                                  
                                                                 
  //================================================================
  begsr $inzsr;                                                     
  //================================================================
  endsr;                                       
                                          
  //================================================================
  begsr $Main;                                           
  //================================================================
      clear outAddress;                 
                                                             
      if inUser = *blanks;                  
          inUser = #User;                
      endif
 
      chain inUser QAOKL02A;                            
      if not %found;                        
          leavesr;                                     
      endif;    
                                   
      chain (WOS1DDEN:WOS1DDGN) QATMSMTPA;            
      if not %found;                  
          leavesr;                  
      endif
 
      outAddress = %trim(SMTPUID) + '@' + %trim(DOMROUTE);  
      outAddress = %xlate(UCase:LCase:outAddress);
 
  endsr;                                      


System catalogs are a great place to get information about your iSeries objects and are an alternative to APIs and command outfiles. Just be sure to use them carefully.

Doug Eckersley is the chief iSeries developer at Dominion Homes in Dublin, Ohio. He has over 16 years of application development experience and is the co-author of Brainbench’s RPG/IV certification test.

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: