files handing

-
FILE HANDLING
Basic terms in file handling:
1. Files
2. Records
3. Fields.
4. Physical file.
4. Logical files.
FILES: it is collect of records.    Ex: student file, employments file.
RECORDS: it is collect of fields that are used to describe an entity. One or more fields from together are called records.     Ex: student ID, student name.
FIELDS:  A set of characters are combined together called as information.
PHYSICAL FILE: it is the information that exists on the external device. It is known as external devices.
LOGICAL FILE: it is the information that is used by the program. In COBOL program one file can be handled at one time only.
Difference between physical and logical file:

Physical file
Logical file
1.      Occupies the portion of memory. It contains the original data.
2.      It contains 1 record format.
3.      Can exist even without logical file.
4.      If there is a logical file for physical file, the physical file can’t delete until and unless we delete logical file.
1.      Does not occupy any memory space.  Does not contain any data.it loads itself at run time as per the defined access path.
2.      It contains 16 record formats.
3.      Can’t exist without physical file.
4.      If there is a logical file for a physical file, the logical file can be deleted without delete the physical file.
.

Files are identified by file name.
Records are identified by record name.
Fields are identified by field’s name.
WORKING WITH FILES:
1. Declaration of files.
2. Processing of files.

Declaration of files is done in environment and data division.
Processing of files is done in procedure division.
Declaration of files:
ENVIRONMENTAL DIVISION.
INPUT-OUTPUT SECTION
FILE CONTROL
               SELECT LOGICAL FILE NAME ASSIGN TO PHYSICAL NAME.
              ORGANIZATION IS SEQUENTICAL/INDEXED/RELATIVE.
            ACCESS MODE IS SEQUENTICAL/DYNAMIC/RANDOM.
            RECORD KEY/RELATIVE KEY IS ----------------------.
            FILE STATUS IS FS.
DATA DIVISION.
FILE SECTION.
FD LOGICIAL FILE NAME.
01 TR-DATA-FILE.
       02 NAME PIC X(09).
WORKING STORAGE SECTION.
01 WS-FS PIC X(01).

Processing of files.
STEPS
1. OPEN THE FILE.
2. LOGICAL OPERATON LIKE WRITE, READ, REWRITE, UPDATE.
3. CLOSE THE FILE.
OPENING MODES:
INPUT MODE: READ (READ DATA FROM THE FILE).
OUTPUT MODE: WRITE (WRITE THE DATA INTO THE FILE).
INPUT-OUTPUT MODE: READ AND REWRITE (UPDATE). AND DELETE.
EXTEND MODE: WRITE (APPEND THE RECORD).

PROCEDURE DIVISION.
OPEN MODE LOGICAL FILE NAME.
LOGICAL FOR WRITE/READ/REWRITE.
CLOSE LOGICAL FILE.








Comments

Post a Comment

Popular posts from this blog

COBOL + DB2 complication process.

-
Image
There are various step involved before we run/execute a COBOL + DB2 program.   Below step are the various steps.   Precompile.   Compile.   Link edit.   Bind.   Package & plan. Step 1: Precompile               COBOL compiler did not understand about SQL statement so, it undergoes to precompile. In precompile.     Expands all include copybooks which are written in program.     Extracts all SQL statements into DBRM and SQL statement are convert into call statements.    Generates time-stamp for modified source codes and DBRM .there are checked at run time.   Check syndicated error of SQL statements and validates the fields based on the table declaration from dclgen copybook.    Notes: precompilation process can be executed even if DB2 is down. DSNHPC    ----------- It is the program used for precompilation. Step 2:  Compile            It is same as normal COBOL compilation.it takes modified source as input and compilers.  IGYRCTL --
Read more

ABEND list for JCL

-
what is ABEND?   An ABEND (abnormal end) is an exception condition which results in the abnormal termination of a program or software. It is a common terminology used in the mainframe world where a JCL terminates with an error code.  S0CB -    Attempting to divide by 0 and not using ON SIZE ERROR S002 -    Very large record length/ wrong record length Sx22 -   Job has been cancelled. The value of x will vary depending on the way the job was  cancelled. . S222 -    Means job was cancelled by a user or operator without a dump.                If a TSO session times out you will probably get an S522 ABEND code. S222 -    The job was cancelled (by subsystem or operator) because it violated               Some restriction. S522 -    JOB or TSO session exceeded maximum job wait time OR               Operator did not mount the require tape within allowed time limit    S806 -    Load module not found SB37
Read more

difference between jes2 and jes3

-
JES2 JES3       1.        Decentralization.       2.        Every processor the incoming job individually.       3.        It is prestep allocation.       4.        Dataset allowed before step is executed.       5.        It is a local process.       6.        Control statement (//*). 1. Centralization. 2. It control process and assign job to sub processor. 3. It is prejob allocation. 4. Dataset allowed before job is schedule. 5. It is global process. 6. Control statement (/*).
Read more