AS400 interview questions and answers-Part 1

1. What does ‘AS’ in AS400 stands for?

Ans: Application system.

2. What is ‘LPAR’?

Ans: OS/400 Version 4, introduced a feature LPAR (Logical PARtitioning) which facilitates running multiple operating systems simultaneously on one IBM System i unit ensuring that one OS doesn’t interfere other’s system resources/memory.

3. What is library is AS400? What are the types of library?

Ans: When we execute a command or call a program, the AS/400 must know where to find the command or program and the answer is library. A Library is a collection of objects. QSYS is the only library that contains other library. QSYS is the root library where the entire user defined/ system defined library is created. System supplied libraries begin with the letter "Q" or "#".

Library list types:

System library: All IBM supplied library e.g. QSYS, QHLPSYS, QUSRSYS…

Product Library: Whenever Ibm product is used it is added to the library automatically and is removed itself when the job completes.

Current Library: Current library is the working library i.e. all the work done by you is stored in current library.

User Library: Non-IBM supplied i.e. created by the user.

For more information related to library and library commands: Click here...

4. Which library gets first loaded into the system when we login?

Ans: QSYS

5. What is the purpose of QGPL library?

Ans:

QGPL (General Purpose Library) is subpplied by IBM. Normally, commonly used objects are placed in QGPL. So, that it can be used by all the users signed into that system.

e.g.

We can use QGPL library in below cases:

Create an Output queues in QGPL so that the common printer can be used by everyone.

Create Commands in QGPL so that it can be used by all.

Transfer object to QGPL LIBRARY on remote system, so that those transferred objects can be used by different users.

In many cases, when you do not specify a library while creating object, then system will create object in QGPL. e.g.

DSPFD FILE(ACCOUNT) TYPE(*MBR) OUTPUT(*OUTFILE) OUTFILE(*LIBL/OUT11111)  

After running above command, OUT11111 will be placed in QGPL as we mentioned *LIBL in library which is not specific. Hence system uses this general purpose library QGPL. Hence, this General purpose library is used by System as well as by users.

But, it is always advised to use your personal library instead of using QGPL.

6. How can we see all the objects and its sizes in a library?

Ans: By using the command DSPLIB.

Example:  DSPLIB IROBO1

     It gives you the information of all objects that resides in the library with it size.

                                Display Library                                
                                                                               
 Library  . . . . . . :   IROBO1          Number of objects  . :   8            
 Type . . . . . . . . :   PROD            Library ASP number . :   1           
 Create authority . . :   *EXCLUDE        Library ASP device . :   *SYSBAS     
                                                                               
 Type options, press Enter.                                                    
   5=Display full attributes   8=Display service attributes                    
                                                                               
 Opt  Object      Type      Attribute               Size  Text                 
      PRINT1PGM   *PGM      RPGLE                 131072  rpgle program for pri
      ACCOUNT     *FILE     PF                     49152  ACCOUNT RELATED INFOR
      PRINT1      *FILE     PRTF                    4096  PRINTER DDS RLU GENER
      QCLSRC      *FILE     PF                      8192  Sources CL-Programs  
      QDDSSRC     *FILE     PF                      8192  DDS-Sourcen          
      QRPGLESRC   *FILE     PF                     69632                       
      QRPGLESRC2  *FILE     PF                     65536                       
      QRPGSRC     *FILE     PF                      8192  SOURCE PHYSICAL FILE 
                                                                                
                                                                               
                                                                               
                                                                         Bottom
 F3=Exit   F12=Cancel   F17=Top   F18=Bottom                      

7. What is source physical file?

Ans: Source physical file is a file which contains the sources of different types of objects. There can be up to 32768 members. Source physical file is an object. But the source member is not an object. When we compile the member, the object is created for that source. Command used is CRTSRCPF.

8. How to see all members of a file?

Ans: By using the command shown below:

9. How to see all record formats used in a file?

Ans: By using the command shown below:

10. How to change the record size of a physical file?

Ans: By using the command below:

We change the highlighted part to change the size of a file.

                          Change Physical File (CHGPF)                          
 
                                                                               
 Type choices, press Enter.                                                    
 
                                                                               
 Physical file  . . . . . . . . .                 Name                         
   Library  . . . . . . . . . . .     *LIBL       Name, *LIBL, *CURLIB         
 
 System . . . . . . . . . . . . .   *LCL          *LCL, *RMT, *FILETYPE        
 
 Source file  . . . . . . . . . .   *NONE         Name, *NONE                  
   Library  . . . . . . . . . . .                 Name, *LIBL, *CURLIB          
 
 Member size:                                                                  
 
   Initial number of records  . .   *SAME         1-2147483646, *NOMAX, *SAME  
   Increment number of records  .   *SAME         0-32767, *SAME               
   Maximum increments . . . . . .   *SAME         0-32767, *SAME 

11. How can we arrange duplicate records in a file?

Ans: For this we will use file level keywords FIFO/LIFO/FCFO in the physical file.

FIFO: The duplicate key records will retrieved in first in first out order.    
LIFO: The duplicate key records will retrieved in last in first out order.     
FCFO: The duplicate key records will retrieved in first changed first out order.

12. How to refer another file to define a new field in a physical file?

Ans: below is an example, we are going to use the file REFER to get the field definition for new file.

USE OF REFERENCE                                                  

 
Columns . . . :    1  71           Browse                        AMINEM/DDSSRC
SEU==>                                                                   REFER
FMT PF .....A..........T.Name++++++RLen++TDpB......Functions++++++++++++++++++
       *************** Beginning of data *************************************
0002.00      A          R REF
0003.00      A            RAC1           2P 0       COLHDG('LEVEL ID')
0004.00      A            RAC2           3P 0       COLHDG('ORG CODE')
0005.00      A            RAC3          12P 0       COLHDG('ACCOUNT NUM')
0006.00      A            RAC4           3A         COLHDG('ACCOUNT CURRENCY')
0007.00      A            RPOSTCODE      2P 0       COLHDG('POST CODE')
0008.00      A            RCOUNTRY       3P 0       COLHDG('COUNTRY CODE')
0009.00      A            RNAME         20A         COLHDG('NAME')
0010.00      A            RDATE          3P 0       COLHDG('DATE')
          ****************** End of data ****************************************

Now we can refer the file ‘REFER’ to take the field definition in the new file.

Columns . . . :    1  71           Browse                        AMINEM/DDSSRC 
SEU==>                                                                  USEREF 
FMT PF .....A..........T.Name++++++RLen++TDpB......Functions++++++++++++++++++        
*************** Beginning of data *************************************
0002.00      A                                      REF(REFER)                 
0003.00      A          R USEREF                                               
0004.00      A            ACCLVL    R               REFFLD(RAC1 REFER) >>>>>>  field name and
0005.00                                             ALIAS(ACC_LVL_ID)     referred file name
0007.00      A            ACCORG    R               REFFLD(RAC2 REFER)           
0008.00                                             ALIAS(ACC_ORG_CODE)        
0009.00      A            ACCNUM    R               REFFLD(RAC3 REFER)         
0010.00                                             ALIAS(ACC_NUM)             
0011.00      A            ACCCUR    R               REFFLD(RAC4 REFER)         
0012.00                                             ALIAS(ACC_CUR)             
0013.00      A            ACCNAME   R               REFFLD(RNAME REFER)        
0014.00                                             ALIAS(ACC_NAME)            
 
  ****************** End of data ****************************************

13. Can LEVEL CHECK ERROR occur if we do CHGPF?

Ans: It depends on the value that we have set for LVLCHK (Record format level check) attribute. If its value is *YES then the record format level identifier is checked when the file is opened and if it doesn’t match it throws the error. If its value is *NO, then the record format level identifier is not checked, hence no error.