SORT Statement
SORT statement is a powerful statement used for sorting files internally within the program. It's mainly useful in batch processing, where large amounts of data need to be sorted before further processing.
SORT operation differs from other programming languages because it can work directly on input and output files without loading the data. It can be coded anywhere in the procedure division except in the declarative portion.
Syntax -
1----+----2----+----3----+----4----+----5----+----6
SORT work-file-1 ON ASCENDING|DESCENDING KEY key-1
[ASCENDING|DESCENDING KEY key-2 ...]
[USING input-file1]
[GIVING output-file]
[COLLATING SEQUENCE IS alphabet-name]
[USING input-file2 ...]
[INPUT PROCEDURE IS para-1 THRU para-2]
[OUTPUT PROCEDURE IS para-3 THRU para-4]Parameters -
- work-file-1 - The name of the sort work file. It's a logical file and does not correspond to any physical file.
- ASCENDING|DESCENDING KEY - Specifies the sort order. You can sort on multiple keys.
- key-1, key-2, ... - The data item(s) on which to sort.
- USING input-file1, input-file2, ... - The name of the input file to be sorted.
- GIVING output-file - The name of the output file where the sorted data will be written.
- COLLATING SEQUENCE IS alphabet-name USING file-4 ... - Optional. Defines the sequence in which data is sorted. For instance, specify an EBCDIC or ASCII collating sequence.
- INPUT PROCEDURE - Optional. A procedure is executed for each record of the input file before sorting.
- OUTPUT PROCEDURE - Optional. A procedure is executed for each record of the sorted file.
Files used in sort process -
Three files are used in the sorting process −
- Input file
- Work file
- Output file
Sort processing steps -
- It opens work file in I-O mode, input file in INPUT mode, and output file in OUTPUT mode.
- Transfers the records from input file to the work file.
- Sorts the sort file based on the order coded with key-1.
- Transfers the sorted records from work file to output file.
- Closes the input, output files and releases (deletes) the work-file.
Practical Example -
Scenario - Let us assume we have an employee file that contains employee information unsorted. The file should be sorted based on the employee number (1-5 characters) in ascending order.
Input (MATEPK.EMPFILE.NSINPUT1) -
----+----1----+----2----+----3----+----4----+-- E0004EMPLOYEE4 TL DEPT1LOC1 0000050000 E0002EMPLOYEE2 MGR DEPT1LOC1 0000080000 E0006EMPLOYEE6 SE DEPT1LOC1 0000034000 E0001EMPLOYEE1 DIR LOC1 0000100000
Code -
----+----1----+----2----+----3----+----4----+----5----+
...
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT EMPFILE1 ASSIGN TO INPUT1.
SELECT EMPFILEO ASSIGN TO OUTPUT1.
SELECT WORKFILE ASSIGN TO WORK1.
...
DATA DIVISION.
FILE SECTION.
* Use declarations from SORT example
...
PROCEDURE DIVISION.
SORT WORKFILE
ON ASCENDING KEY WORK-EMP-NUM
USING EMPFILE1
GIVING EMPFILEO.
...JCL -
///MATEPKRJ JOB MSGLEVEL=(1,1),NOTIFY=&SYSUID //* //STEP01 EXEC PGM=SORTFLS //STEPLIB DD DSN=MATEPK.COBOL.LOADLIB,DISP=SHR //INPUT1 DD DSN=MATEPK.EMPFILE.NSINPUT1,DISP=SHR //OUTPUT1 DD DSN=MATEPK.EMPFILE.NSOUT1, // DISP=(NEW,CATLG,DELETE), // SPACE=(TRK,(3,2),RLSE), // UNIT=SYSDA, // DCB=(DSORG=PS,RECFM=FB,LRECL=47,BLKSIZE=470) //WORK1 DD DSN=&&TEMP, // DISP=(NEW,DELETE,DELETE), // SPACE=(CYL,(10,5),RLSE), // UNIT=SYSDA, // DCB=(DSORG=PS,RECFM=FB,LRECL=47,BLKSIZE=470) //SYSOUT DD SYSOUT=*
Output (MATEPK.EMPFILE.NSOUT1) -
----+----1----+----2----+----3----+----4----+-- E0001EMPLOYEE1 DIR LOC1 0000100000 E0002EMPLOYEE2 MGR DEPT1LOC1 0000080000 E0004EMPLOYEE4 TL DEPT1LOC1 0000050000 E0006EMPLOYEE6 SE DEPT1LOC1 0000034000