Logical Files:
Overview:
This
module enables the student to understand the concept of Logical File.
Outline:
Topics
covered,
·
Logical
file creation
- Concept
of Keyed & Sequential access
- Commands
related to files
Objective:
By the end of this module, the student should be
able to:
- Create
a Logical file
- Understand
the part of Logical files.
- Commands
related to files.
Logical File:
A logical file is provide access the data
stored in one or more physical files. The features unique to logical files
include the following:
- Logical files do not contain data.
- Access one or more physical files in an arrival sequence or in
any single or multiple field (key) value order.
3.
A physical file may be
processed by any number of logical files.
- Two or more logical
files may share the same access path.
- Omit and select criteria may be specified in a logical file to
process only the required physical file data.
- A logical file may include multiple record formats. Each format
however must relate to one or more physical files and include at least one
key field.
- One logical file with multiple record formats may process only
the required physical file data.
- A logical file with multiple record formats may be used to
process the data from more than one physical file. The file record formats
accessed may be of different lengths.
9 During processing a physical file’s field
attributes may be changed by a logical file. However, the data stored in the
physical file not be modified.
Logical files may be specified as either nonjoin
or join. A nonjoin logical file processes each record individually from one
or more physical files. Join logical files however create a single record from
the selected fields from two or more physical files.
The type of logical file (nonjoin or
join) specified is determined in the related DDS coding. In the following text,
the processing logic and DDS syntax for nonjoin logical files are introduced
first, followed by the coding requirements associated with join logical files.
NONJOIN LOGICAL FILES (ONE-RECORD
FORMAT)
- File level entries (optional)
- Record level entries
- Field level entries (optional)
- Key field level entries (optional)
- Select/omit level entries (optional).
Non-join logical files may specify more
than one record format. If two or more physical files with different record
formats are to be used by a logical file, separate PFILE keywords must be
specified. When the record formats are the same, only one PFILE keywords is
required. A maximum of 32 physical files may be referenced in one PFILE
keyword.
When two or more physical files with a
logical file accesses different record formats. *NONE may be specified as a key
field substance for any of the following conditions:
- The related keyfields from the physical files do not have the
same attributes.
- The key fields from the physical files have the same
attributes, but they are not to be merged and sequenced together.
Specify
the entries in the following order to define a simple or multiple format
logical file:
1. File-level entries (optional)
IN NEXT STEP YOU HAVE TO WRITE SOURCE TYPE AS ‘LF’ &
SOURCE MEMBER –
Start Source Entry
Utility (STRSEU)
Start Source Entry
Utility (STRSEU)
Type choices, press Enter.
Source file
. . . . . . . . . . > MYDDS
Name, *PRV
Library
. . . . . . . .> PB01U01D
Name, *LIBL, *CURLIB, *PRV
Source member
. . . . . . . . . LSTUDENT Name, *PRV, *SELECT
Source type
. . . . . . . . . . LF Name, *SAME, BAS, BASP...
Text ‘description’ . . . . . . . ‘LOGICAL FILE FOR STUDENT’
Bottom
F3=Exit
F4=Prompt F5=Refresh F12=Cancel
F13=How to use this display
F24=More keys
PRESS ENTER SO THAT YOU
GET THE FOLLOWING SCREEN
Columns . . . : 1
71 Edit SHEET/QSRC
Columns . . . : 1
71 Edit SHEET/QSRC
SEU==>
LSTUDENT
FMT
LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
*************** Beginning of data *************************************
'''''''
'''''''
'''''''
'''''''
'''''''
'''''''
'''''''
'''''''
'''''''
'''''''
****************** End of data ****************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
AFTER TYPING ‘IPLF’
AS SHOWN ABOVE USER GETS THE FOLLOWING PROMPT-
Columns . . . : 1
71 Edit PB01U01D/MYDDS
******************End of data ****************************************
Enter reference file using ‘PFILE(FILE
NAME)’ function key as well as record format name as shown below :
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
Enter key field
of referred physical file :
Columns . . . : 1
71 Edit PB01U01D/MYDDS SEU==> LSTUDENT
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
Press F3 and use option 14 to compile
the above file and create object in PB01U01O and Runqry command for above
logical file gives following output:
Display
Report
Reference file name and key field gives all
field from related physical file. But in logical file user is able to select
particular field as shown below. Just insert the required field name as per
above define sequence:
Columns . . . : 1
71 Edit PB01U01D/MYDDS
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT
FMT
LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
*************** Beginning of data *************************************
'''''''
******************End of data ****************************************
Prompt type . . . LF
Sequence number . . . “”””””
Name
Data Decimal
Type
Name Length Type
Positions Use Functions
F3=Exit
F4=Prompt F5=Refresh
F11=Previous record F12=Cancel
F23=Select prompt F24=More keys
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==> LSTUDENT
FMT LF
.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++ *************** Beginning of data
*************************************
0001.00 A
R SR
PFILE(STUDENT)
****************** End of data
****************************************
Prompt type . . . LF
Sequence number . . .
0001.00
Name Data Decimal
Type
Name Length Type
Positions Use
R SR
Functions
PFILE(STUDENT)
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
F12=Cancel F23=Select prompt F24=More keys
Columns . . . : 1
71 Edit PB01U01D/MYDDS SEU==> LSTUDENT
FMT
LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
*************** Beginning of data *************************************
0001.00 A
R SR
PFILE(STUDENT)
0002.00 K ROLL
****************** End of data ****************************************
Prompt type . . . LF
Sequence number . . .
0002.00
Name Type
Name Length Type
Decimal Positions Use
K ROLL
Functions
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
F12=Cancel F23=Select prompt F24=More keys
Display
Report
Report width . . . . . :
39
Position to line . . . . . Shift to column . . . . . .
Line ....+....1....+....2....+....3....+....
ROLL SNAME CCD
CORS ADD CITY
000001
101 sneha vv
VB pune pune
000002
102 ramesh hh
C mumbai mumbai
000003
103 titu iii
AS mumbai pune
000004
104 rahul AS400
VB pune pune
****** ******** End of report
********
Bottom
F3=Exit F12=Cancel F19=Left F20=Right F21=Split
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT
FMT
LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
*************** Beginning of data *************************************
0001.00 A
R RSTUDENT
PFILE(STUDENT)
0002.00 A ROLL
0003.00 A SNAME
0004.00 A CORS
0005.00 A
K ROLL
****************** End of data *******************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
© COPYRIGHT IBM CORP. 1981,
2002.
Use RUNQRY
command on command prompt to see the output.
Display Report
Also you are able to define multiformat
logical file as shown below:
Columns . . . : 1
71 Edit PB01U01S/MYDDS
HOW TO USE COLHDG & ‘TEXT’ K/W:
Display Report
Report width . . . . . :
19
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....
ROLL SNAME CORS
000001
101 sneha vv
000002
102 ramesh hh
000003
103 titu iii
000004
104 rahul AS400
****** ******** End of report
********
Bottom
F3=Exit
F12=Cancel F19=Left F20=Right F21=Split
Columns . . . : 1
71 Edit PB01U01S/MYDDS
SEU==> LSTUDENT
FMT LF
.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++ *************** Beginning of data
*************************************
0001.00 A
R RS PFILE(STUDENT)
0002.00 A ROLL
0003.00 A SNAME
0004.00 A CORS
0005.00 A
K ROLL
0005.01 *
0006.00 A
R RCORS
PFILE(CORS)
0007.00 A
K CCD
****************** End of data ****************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
Columns . . . :
1 71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT FMT LF
.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
SEU==>
LSTUDENT FMT LF
.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
*************** Beginning of data
*************************************
0001.00 A R RS PFILE(STUDENT)
0002.00 A
ROLL
COLHDG(‘ROLL NO’)
0003.00 A
NAME
TEXT(‘STUDENT DETAIL’)
0004.00 A
CORS
0005.00 A
K ROLL
****************** End of data ****************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
©
COPYRIGHT IBM CORP. 1981, 2002.
OUTPUT OF COLHDG & TEXT KEYWORD :
Display Report
- COMP 2. RANGE 3. VALUE
Display Report
Report width . . . . . : 21
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....2.
ROLL NO SNAME CORS
000001
101 sneha vv
000002
102 ramesh hh
000003
103 titu iii
000004 104
rahul AS400
****** ******** End of report
********
Bottom
F3=Exit
F12=Cancel F19=Left F20=Right F21=Split
HOU
TO USE ABOVE KEYWORD WITH SELECT & OMIT:
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
Display Report
Like
that we are able to use range and value keyword with logical file. Now use of
omits keyword with logical file.
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT
Output of above ‘omit’ keyword is as
shown below see it using RUNQRY command on command line:
Display
Report
You can use this k/w on one field &
one file as shown below
Columns . . . : 1
71 Edit PB01U01D/MYDDS
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle F16=Repeat find F17=Repeat change F24=More keys
Display
Report
Use of value keyword :
columns . . . : 1
71 Edit PB01U01D/MYDDS
Output of this keyword is where roll number
having value 102 gets omitted.
Display Report
Report width . . . . . :
21
Columns . . . : 1 71
Edit
PB01U01D/MYDDS
SEU==>
LSTUDENT
FMT
LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
***************Beginning of data *************************************
0001.00 A
R RS
PFILE(STUDENT)
0002.00 A ROLL COLHDG(‘ROLL NO’)
0003.00 A NAME TEXT(‘STUDENT DETAIL’)
0004.00 A CORS
0004.01 A
K ROLL
0005.00 A
S ROLL COMP(GT
102)
****************** End of data ****************************************
Prompt type . . . LF Sequence number . . . 0004.01
Name Data Decimal
Type
Name Length Type
Positions Use
S ROLL
Functions
COMP(GT 102)
F3=Exit
F4=Prompt F5=Refresh F11=Previous record
F12=Cancel F23=Select prompt F24=More keys
Display Report
Report width . . . . . :
21
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....2.
ROLL NO SNAME CORS
000001
103 titu iii
000002
104 rahul AS400
****** ******** End of report
********
Bottom
F3=Exit
F12=Cancel F19=Left F20=Right F21=Split
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT
FMT
LF.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
***************Beginning of data *************************************
0001.00 A
R RS
PFILE(STUDENT)
0002.00 A ROLL COLHDG(‘ROLL NO’)
0003.00 A NAME TEXT(‘STUDENT DETAIL’)
0004.00 A CORS
0004.01 A
K ROLL
0005.00 A
O ROLL COMP(GT 102)
****************** End of data
*************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
© COPYRIGHT IBM CORP. 1981, 2002.
Display
Report
Report width . . . . . :
21
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....2.
ROLL NO SNAME CORS
000001
100 ABC AS400
000002
101 sneha vv
****** ******** End of report
********
Bottom
F3=Exit
F12=Cancel F19=Left F20=Right F21=Split
Columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT
FMT LF .....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
************* Beginning of data *************************************
0001.00 A
R RS
PFILE(STUDENT)
0002.00 A ROLL COLHDG(‘ROLL NO’)
0003.00 A SNAME TEXT(‘STUDENT
DETAIL’)
0004.00 A CORS
0005.00 A
K ROLL
0006.00 A
O ROLL
COMP(EQ 102)
0007.00 A
S ROLL
COMP(GT 100)
**************** End of data ****************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle F16=Repeat find F17=Repeat change F24=More keys
© COPYRIGHT IBM CORP. 1981, 2002.
OUTPUT OF THIS COMPARISON IS
Display
Report
Report width . . . . . :
21
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....2.
ROLL NO SNAME CORS
000001
101 SNEHA VV
000002
103 titu iii
****** ******** End of report
********
Bottom
F3=Exit F12=Cancel F19=Left F20=Right F21=Split
columns . . . : 1
71 Edit PB01U01D/MYDDS
SEU==>
LSTUDENT FMT LF
.....A..........T.Name++++++.Len++TDpB......Functions++++++++++++++++++
***************Beginning of data *************************************
0001.00 A
R RS
PFILE(STUDENT)
0002.00 A ROLL COLHDG(‘ROLL NO’)
0003.00 A NAME TEXT(‘STUDENT DETAIL’)
0004.00 A CORS
0004.01 A
K ROLL
0006.00 A
O ROLL
VALUES(102)
0007.00
A S ROLL COMP(GT 100)
****************** End of data
****************************************
F3=Exit
F4=Prompt F5=Refresh F9=Retrieve
F10=Cursor F11=Toggle
F16=Repeat find F17=Repeat change F24=More keys
Display Report
Report width . . . . . :
21
Position to line . . . . . Shift to column . . . . . .
Line
....+....1....+....2.
ROLL NO SNAME CORS
000001
101 sneha vv
000002
103 titu iii
****** ******** End of report
********
Bottom
F3=Exit
F12=Cancel F19=Left F20=Right F21=Split
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