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#COBOL READ FILE HOW TO#

It contains both random and sequential access.The record in these files can be accessed by – RRN – relative record number.Also known as relative record data set – RRDS – file.We can delete a particular record in an indexed file, but the record can not be deleted physically, but the particular memory location can not be accessed for the record. The key field can not be updated in the indexed file. KEYS are case sensitive, i.e., S007 is not the same as s007 To write the record with key S007, we must write all the records with key less than S007, To write an indexed file, we must write the records in increasing order of the keys. In these files, the organization is always indexed.In the index file, these key must be uniquely defined.Access mode can be sequential as well as random.These records can be accessed in any order irrespective of position using the key.They use alphanumeric characters as the key.These files can be accessed much faster, and the access is done using key values.

These are also known as text files to write a report file, the file should be define as a line sequential file.

A line sequential file is a special type of sequential file where a carriage return separates each record ( X” 0D”) or line feed ( X “0A”) at the end of the last non-space character these always contain variable-length records.

If there is a simple read and write function and very little search of the record is required, these files are recommended.

These files have either fixed or variable length.

New records are added to the end, i.e., first come, first serve.

You have to read the N-1th before proceeding to the Nth.

Store records in a sequential manner, i.e., one after another, stacked.and lastly, these fields contain information about the data. Further, each record is divided into fields. From that record on wards continue reading the file in reverse order.Files are used in Cobol to store data in the form of a disk or tape. Issue another READPREV which actually reads the last record of the file.Then issue a READPREV which reads the HIGH-VALUES record. Generally, KSDS files are established with LOW-VALUES and HIGH-VALUES records as the first and last records of the file respectively.In this case we cab easily do the reverse order reading of the file.

#COBOL READ FILE HOW TO#

How to Read a VSAM file from last record to first Go on Issuing the read previous commands until all the required daata is processed or EOF.ĮND-EXEC. So to avoid these kind of errors, it is always recommended to use read next command before the read prev.Įstablish the Starting point EXEC CICS STARTBR READPREV can be used immediately after the STARTBR, but in this case specified key using STARTBR should exist in the file otherwise it gives error. To read a record in reverse order starting from a key needs to establish a starting point first which can be done using STARTBR, then READNEXT and READPREV does the backwards reading. READPREV command is used for this purpose. Apart from reading forward, VSAM KSDS file can be read Backwards starting from a specified Key value.