Introduction
- Different access modes are used for each organization scheme.
- These access modes are used to define accessing way of the file depending on the requirement of the program.
1. Sequential Access
When the access mode is sequential, the method of record retrieval changes according to the selected file organization.- For sequential file, records are accessed in the same order as they are inserted in the sequential file.
- For indexed file, the parameter used to get the records using the record key value.
- For relative files, Relative record keys are used to fetch the records.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS SEQUENCIAL
ACCESS MODE IS SEQUENCIAL
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS INDEXED
ACCESS MODE IS SEQUENCIAL
RELATIVE KEY IS rec-key1
ALTERNATE RECORD KEY IS rec-key2
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS RELATIVE
ACCESS MODE IS SEQUENCIAL
RELATIVE KEY IS rec-key1
2. Random Access
In random access mode, the method of record retrieval is changed according to the selected file organization.- The random access mode is used for the INDEXED AND RELATIVE files only.
- For the INDEXED file, records are accessed as the value placed in a key field. The key field is a primary key or alternate key.
- For relative files, records are fetched through relative record keys.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS INDEXED
ACCESS MODE IS RANDOM
RELATIVE KEY IS rec-key1
ALTERNATE RECORD KEY IS rec-key2
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS RELATIVE
ACCESS MODE IS DYNAMIC
RELATIVE KEY IS rec-key1
3. Dynamic Access
- In dynamic access mode, both sequential and random access are supported in the same program.
- This access mode is used for all types of files.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS SEQUENCIAL
ACCESS MODE IS DYNAMIC
RELATIVE KEY IS rec-key1
ALTERNATE RECORD KEY IS rec-key2
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT file-name ASSIGN TO dd-name
ORGANIZATION IS RELATIVE
ACCESS MODE IS DYNAMIC
RELATIVE KEY IS rec-key1
