Monday, 6 August 2012

as400 interview questions asked ibm


IBM AS-400 Interview Questions-->3



61. When would you prefer logical file than OPNQRYF?
The physical file you are working with very large, creating and using a logical file will allow an application to perform faster than using an open query file.   Since access paths created by open query files are temporary, applications that use an access path frequently will be more efficient using a logical file, since the access path will not have to be rebuilt every time the file is open.

62. What the purpose of the keywords FIFO, LIFO, FCFO?
These keywords are used at file level.   The purpose of each one is described below:
         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.

63. What is the difference between regular logical file and join logical file?
Regular logical file contains more than one record format.
          Record format name in regular logical file should be same based on the physical file.
Join logical file contains only one record format.
          Record format name in join logical file should be different.
          Through logical file we can made changes in physical file.
Through join logical file we can't made changes in physical file.

64. Distinguish between logical file and physical file?
  Physical file contains only one record format.
  Logical file contains more than one record format.
  Physical file contains actual data.
  Logical file doesn't contains data but it provides view from the physical file.

65. What is field reference file?
Field reference file is a file, which contains field definitions and descriptions, and it doesn't have member.   Physical contains data derived by the field reference file.

66. What is the necessary keyword used in a physical file to refer field definitions from the field reference file?
REF which is a file level keyword is necessary to define at file level in a physical file.  The syntax is as follows:  REF (library name/name of the field reference file)

67. What is the purpose of reorganizing the physical file i. e. , RGZPFM?
Even if you delete the records in a physical file through the program, still the space used by the deleted records not used by the other purpose.  Hence using RGZPFM command we can compress the deleted records space.

68. What is the purpose of CHGPF (Change physical file) command?
CHGPF command is used to change the attributes of a physical file.   Attributes like
   * Maximum number of members
   * Member size
   * Level check enforced
   * Open data path is shared
         
69. What is purpose of declarative statement DEFN?
Depends on the factor 1 value it will do two things:
* If the factor1is *LIKE then DEFN opcode defines the new field based on the attributes old field.
* If the factor 1 is *NAMVAR then DEFN opcodes defines the field as a data area.

70. What is the purpose of SFLNXTCHG keyword in a subfile?
This is a subfile record format keyword.   If you perform read on the subfile, the internal indicator MDT (modified data tag) is automatically set off by the system.  If you again perform read on the same records, records won't be read.   Because internal indicator MDT would be off.  Hence you should be explicitly set on the MDT by SFLNXTCHG keyword.

71. What is the difference between Array and Table?
Array: Array is stored any where in the body of the input records.
Table: Table is stored at the beginning of the input records.
Array: We can access all the elements in array by specifying the array name.
Table:  Only one table element can be accessed at a time.
Array:  Array can be searched randomly.
Table:  Table can be searched consecutively.

72. What are the different types of access paths maintained on the file?
Immediate: All the access paths (open and close) associated with a file will be updated whenever changes made to a file.
Rebuild: only open access paths will update whenever changes made to the file.  Rebuild takes place whenever remaining access paths will be open.
Delay:  Rebuild will not take place.

73. How can you identify End of file in CLP program?
With the help of MONMSG MSGID (CPF0864) we can identify end of file in clp program.

74. What is the difference between production library and test library?
In debug mode, the file exists in production library not allowed to update.
In the other hand, the file exists in test library allowed to update.

75.   What is message subfile?
Message subfile is special file contains multiple messages taken from program message queue and placed in message sub file for display on the screen.

76. What are necessary keywords to code message subfile?
SFLMSGRCD, SFLMSGKEY, SFLPGMQ

77. What is the difference between SETON LR and RETRN?
If you specify SETON LR, all the files used in program will be closed.
If you specify RETRN, all the files used in program will remain open.

78. When will you use OPEN and CLOSE opcodes in RPG program?
If you specify the letter "U" at columns 73 - 74 in a file description specification indicating that user control on a file.  Hence we have to explicitly open and close the file in a program.

79. What is difference between fully procedural file and primary file?
In primary file the records will be read and processed from beginning to end.   This order   is not changed.
In fully procedural file the records will be read and processed in any order.   The logic flow is controlled by the opcodes   in RPG program.

80.What is the difference between externally described file and program described file?
The field definitions and descriptions are defined out side of the program in a externally described     file.  The field definitions and descriptions are defined in side the program in a program described file.

81. How many primary files allowed in a program?
Only one primary file is allowed in program.

82. How many secondary files allowed in a program?
More than one secondary files are allowed in a program.

83. What is the purpose of RTVMBRD command?
In order to access the information related to member, we can RTVMBRD command.

84. Define an Interactive Job?
       * A user requests a job.
       * Job is created and job name, job attributes are assigned.
       * Job is placed on a job queue.
     * The sub system QINTER takes the job from the job queue and starts processing.
     * The output generated by the interactive job is placed on the output queue
       * The spool sub system QSPL prints the output.

85.  How can you check the existence of object in a system?
With the help of CHKOBJ clp command, we can find existence of object on the system.
The usage of command in clp is as follows:
      CHKOBJ      OBJ (JBA001DT)    OBJTYPE (*DTAARA)
      MONMSG      MSGID (CPF9801)   EXEC (DO)
      CRTDTAARA   DTAARA (QGPL/JBA001DT) TYPE (*CHAR) LEN (6) +
                             VALUE ('010196') TEXT ('The last day that had    job acct.+
                                      data extracted')
      ENDDO                                                       
      RTVDTAARA   DTAARA (JBA001DT *ALL) RTNVAR (&FROMDATE)
       
  
      The execution of above steps is listed below:
      Steps 
      1:    First it checks the data area object on the system.
     2:   If the data area object not found, the MONMSG command executes     with the help of message identifier, next we can dynamically create the data area.
    3. If the data area object found, control transfers to statement below ENDDO.It is always good CLP programming approach to check the object before you rename, delete the objects on the system.

86. What is the purpose of FRCDTA (Force Data) keyword?
Use this record-level keyword to immediately display a record format, without waiting for the next input or output/input operation.

87.What is the purpose of SFLFOLD and SFLDROP keywords?
SFLFOLD:  To fold the second line of multiple line subfile.
SFLDROP:  To drop the second line of multiple line subfile.

88. What is the function of DSPATR (display attributes) keyword?
Use this field level keyword in display file to specify one or more display attributes for the field you are defining.   You can specify the DSPATR keyword more than once for the same field, and you can specify more than one attribute for the same keyword.   The following are valid attributes:

            For All Fields

          Display
          Attribute                   Meaning
         
          BL                             Blinking field
          HI                              High Intensity
          RI                              Reverse Image
          CS                             Column separator
          ND                            Non Display
          PC                             Position cursor
          UL                             Underline

            For Input-Capable Fields Only

          PR                              Protect contents of field from input keying
          MDT                          Set modified data tag when displayed
          OID                           Operator identification
          SP                              Select by light pen

89. What is the purpose of PUTOVR (Put with explicit override) keyword?
Use this record-level keyword to permit the override of either display file attributes or data contents of specific fields within a record displayed on the work station device.

90. What is the purpose of OVRDTA (Override Data) keyword?
Use this field level keyword with PUTOVR keyword to override the existing the data contents of a field already on the display.
       
91. What is the maximum number of record formats in DSPF?
1024 (One thousand and twenty four)

92. What is the maximum number of fields under a record format of physical file?
8000 (eight thousand)

93. What is the maximum number of parameters allowed in RPG?
255 (Two hundred and fifty five)

94. What is the maximum number of parameters allowed in CLP?
43 (Forty three)

95. What is the maximum number of subroutines allowed in RPG?
254 (Two hundred and fifty four)

96. What is the maximum number of files allowed in RPG?
50 (Fifty including eight printer file)

97. What is maximum number of Arrays allowed in RPG?
250 (Two hundred and Fifty )

98. Where can you specify an indicator in LOKUP operation?
In  ‘EQ’  position.

99. What is a Member?
It is a subset of data records of a physical file.

100. What is a Physical file?
Physical file nothing but a table contains a only one record format in which we can describe the field definitions and descriptions.

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