Interview Question and Answer – Operating System OS400

AS400

Jan 12

Twenty years ago these are the kind of things you had to know to work on the old AS400 systems. I found these on an old dusty corner of my homeserver. Enjoy the trip down memory lane or to use old RPG lingo AS400NERD CABEQ ‘1’  START

OS/400

What is DDM ?
Distributed Data Management is a function of the OS/400 that allows an application program or user on one system to use database files stored on remote system.

What are the facilities available on AS/400 for self-learning?
on-line education, Q&A Database and Help.

What is an Object?
An object is any thing that exist in and occupies space in storage and on which operation can be performed.

What are the different types of Objects available in the AS/400?
Libraries, Folders, Files, Programs, Combined definitions, Queues, User Profiles.

How are the objects stored in AS/400?
All objects are stored on AS/400 in a single level storage. In this method all objects are referenced by one virtual address which is translated into a physical address whether it is an auxiliary storage or main memory.

What is a library in AS/400?
A library in AS/400 is an object that serves as a repository for other objects.

Name few IBM supplied libraries?
QGPL, QTEMP, QUSRTOOL, QSYS, QRPG & QCBL.

What is a library list?
A list that indicates libraries used for the process and the order in which it has to be searched. System identifies it in *LIBL.

How many libraries can be there in a library list?
Total 40 (15 system and 25 application).

Where is the system part of the library list stored?
In SYSVAL (QSYSLIBL)

What is a Folder?
A Folder is a named object that is used as a directory for documents and other folders. Folders can be filed with in another folder.

What are the different Application Development Tools available on AS/400?
SEU, RLU, PDM, SDA, QUERY

What are the levels of security on AS/400?
10,20,30,40,50

What is error severity?
Error severity determines the level of severity that is required to terminate the job.

What is a User Profile? What are the various classes?
User profile is an object which identifies a user to the system. It contains user name, Password, Owned objects, Authorized objects, Scheduling priority, Special authority, Initial program Job description. Security officer, Programmer, Workstation, System operator, Programmer services Rep & Customer engineer.

What is Group Profile?
It is similar to User Profile, but the attributes specified is applicable to an entire group.

What are the different types of queues in AS/400?
Job queue, Message queue, Output queue, Data queue.

What are JobQ and PrintQ ?
JobQ : An object that contains a list of batch jobs waiting to be processed by the system.
PrintQ: An object that contains a list of spool files to be written to a printer device.

What is a Spool file? Why is it required?
A file that holds output data to be processed, such as information waiting to be printed.

What is a Job? What are the attributes of a job?
A job is the basic unit of work on AS/400
The attributes are:
Job Number: Unique system generated sequential number
Job Name : Any user defined name (Max. 10 char)
User Name: Who initiated the job?

What is job description?
A job description defines the environment in which a batch/interactive job is to be executed.

What is the difference between Interactive & Batch job?
Interactive Job: Job started for a person who signon to a workstation.
Batch Job: A predefined group of processing actions submitted to the system to be performed.

What is a Group Job?
Group Job is attached to one workstation and a user. There should be an initial group job and it can be branched to many other group jobs. The group jobs can have different library lists and different output, message queues. Group Job is useful in enhancing the programmer’s productivity. It is as though logging into the same user-id many times.

What are the two main attributes which govern the execution of a job?
Run time priority and Time slice.

What is a sub-system?
Sub-Systems are specific user defined partitions of the CPU where various jobs may be executed. One subsystem can have more than one active job at a time.

What is a device file?
A device file contains the description of how data is to be presented to a program from a device or vice versa. Device file can be Printer, Disk, Tape or Remote system.

What is an ICF file?
A device file that allows a program on the system to communicate with program in other system.

What is a message file?
It is a file which contains the messages of an application. For example all RPG/400 messages are stored in a file; all COBOL/400 messages are stored in a file.

What is a job log?
A record of request submitted to system is a job. The message related to the requests, and the action performed by the system on the log. It is maintained by the system program

What is the purpose of OPNQRYF (Open Query File)?
OPNQRYF is used to select certain records of the database file based on the QRYSLT (Query select) condition.

How do you create files dynamically without DDS?
through OPNQRY.

What command must be executed before executing OPNQRYF command?
OVRDBF.

What is a data area?
A data area is an object used to hold data for access by any job running on the system. A data area can be locked to a single user, thus preventing other users from processing at the same time.

What are the types of data areas?
User defined Data Area, Local Data Area (LDA), Group Data Area (GDA), and Program Initialization Parameter (PIP) Data Area.

What is LDA?
An LDA is created by the system for each job in the system, including autostart jobs, jobs started on the system by a reader, and subsystem monitor jobs.

What is the type and length of an LDA?
*CHAR, 1024 bytes.

What is GDA?
AS400 system creates a GDA when an interactive job becomes group jobs. Only one GDA can exist for a group.

How can you create a user defined data area?
Using CRTDTAARA command.

What are the different ways to input data into a data area?
CHGDTAARA (using CL) Using OUT opcode in RPG

How do you retrieve data from data area?
Using RTVDTAARA command in CL Using IN opcode in RPG.

What are the valid user defined data area types?
CHAR, NUMARIC and LOGICAL.

How can a data area are locked after being updated?
Using OUT *LOCK.

what is the use of data queues?
Data queue is a type of system object that you can create. Data queues are used in program to program communication.

How do you create data queues?
Using CRTDTAQ command.

What are the valid data types for a data queue?
Char, Numeric, and Logical.

What are the two types of read performed on data queues ?
Read with lock, and read without lock.

How do you use DEBUG utility ?
STRDBG program-name UPDPROD(*YES)

What is an authorization list ?
A list of two or more user Ids & their authorities for system resources. The system identifies it as an object type *AUTL.

How do you grant authority for an object?
Using GRTOBJAUT command.

What are the types of object authorities ?
*USE, *CHANGE, *ALL, *EXCLUDE, *AUTL, *OBJEXIST, *OBJMGT, *OBJOPR, *ADD, *DLT, *READ, *UPD.

How do you execute jobs in batch mode?
SBMJOB

What is the use of OVRDBF ?
You can use the Override with Database file (OVRDBF) command to replace the database file named in a CL program or to change certain parameters of the existing database file.

What is the use of OVRPRTF ?
Override with Printer file (OVRPRTF) command is used to override certain parameters of the printer files used in the program or to replace the printer file.

How do you change file attributes such as size, file wait time, record wait time etc., permanently ?
Using CHGPF command.

What is the purpose of CRTCMD ?
To create user defined command.

What is class of service ?
A set of link and node characteristics associated with a session.

How to see active jobs of the system ?
Using WRKACTJOB command.

How do you detect unused spool storage ?
Using Reclaim Spool Storage.

What are the functions of Remote Job Entry (RJE) ?
Allows user of AS/400 system to submit jobs and receive jobs from a host system.

What is the function of RJE Conversion Utility ?
It converts compressed data written to an AS/400 database file to decompressed data written to another AS/400 database, diskette, or device file.

What is the function of the SBMRJEJOB command?
Sends RJE input stream to host system.

What is journaling and commitment control?
Journaling is a function which records the changes in a file in a journal. These record images are used to recover the changes in the file should the system ends abnormally. Commitment control is a function that allows you to define and process a no of changes to database files as a single unit (transaction).

What is the purpose of STRCMTCTL command ?
Starts commitment control for files that are being journal led.

What are the system objects required for journaling?
Journal receiver, journal and PFs to be journal led.

What is CPF ?
Control Program Facility (CPF) is an operating system on S/38.

What is invocation stack ?
List of programs maintained by the system as one program calls another in a series of calls within a single task or job.

What is time slice ?
A finite amount of time in which a job is granted system resources while other jobs are queued.

What is IPL ?
Initial Program Loading (IPL) is run by OS/400 when the system is started.

What does V2R2M0 mean ?
Ver. 2, Release 2 & Modification level 0. This refers to the version of OS/400.

Name the commands used to duplicate a file?
CPYF – Copy File & CRTDUPOBJ – Create Duplicate Object.

Name the command for changing the attributes of a spool file?
CHGSPLFA – Change Spool file Attributes.

Name the command which gives the attributes of a job ?
RTVJOBA – Retrieve Job Attributes.

What is the function of PDM ?
Productivity tool for copying, deleting, scanning, changing & creating source files.

What is the function of SEU ?
A terminal based utility for editing programming language source code.

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About the Author

IBM i Software Developer, Digital Dad, AS400 Anarchist, RPG Modernizer, Alpha Nerd and Passionate Eater of Cheese and Biscuits. Nick Litten Dot Com is a mixture of blog posts that can be sometimes serious, frequently playful and probably down-right pointless all in the space of a day. Enjoy your stay, feel free to comment and in the words of the most interesting man in the world: Stay thirsty my friend.