|Read PF randomly by a record number in CL program|
Overriding the database file
We can use OVRDBF command to override the database file in a CL program and read the PF randomly by a record number i.e. RRN(record relative number). The POSITION keyword/option is used to specify the starting position for reading records from the database file. We can specify *START or *END to read first or last record in a file or we can specify nth record using *RRN.
Below we set position at rrn 2 in the file CLPF1 using OVRDBF command.
Override with Data Base File (OVRDBF) Type choices, press Enter. File being overridden . . . . . FILE > CLPF1 Overriding to data base file . . TOFILE *FILE Library . . . . . . . . . . . Overriding member . . . . . . . MBR Starting position in file: POSITION Retrieve order . . . . . . . . *RRN *RRN-rcd nbr *KEY-nbr key flds 2 *KEY-rec format having key . . *KEY-key value . . . . . . . .
PGM DCL VAR(&NO) TYPE(*DEC) LEN(5 0) DCL VAR(&amo;NM) TYPE(*CHAR) LEN(20) DCLF FILE(CLPF1) OVRDBF FILE(CLPF1) POSITION(*RRN 2) RCVF CHGVAR VAR(&NO) VALUE(&ROLLNO) CHGVAR VAR(&NM) VALUE(&NAME) ENDPGM
Explanation of the above code:
DCL VAR(&NO) TYPE(*DEC) LEN(5 0) DCL VAR(&amo;NM) TYPE(*CHAR) LEN(20)
The DCL command is used in CLP programs to declare the definition for a program variable. *DEC a variable with a packed decimal value which is LEN(5). *CHAR a variable with a character string value which is LEN(20).
This DCLF command is used to declare file named CLPF1 in cl program.
OVRDBF FILE(CLPF1) POSITION(*RRN 2)
This OVRDBF command will override the file CLPF1 and it's position the cursor at relative record number 2 of the file.
This RCVF comamnd is used to recieve file records i.e. to read the file records in CL program specifically. The file being read will be CLPF1 which is declared using DCLF command in the above program.
CHGVAR VAR(&NO) VALUE(&ROLLNO) CHGVAR VAR(&NM) VALUE(&NAME)
This CHGVAR command will change the variable value or evaluate the NO and NM program variables with file fields ROLLNO and NAME of file CLPF1 being read using RCVF command in the CL program.
This ENDPGM command will end the program at this point.
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