In this topic, we described about the Diffence between Files with detailed example.
Below are the differences in between sequential, indexed and relative files.
|Sequential Files||Indexed Files||Relative Files|
|Sequential files are called as QSAM files.||Indexed files are called as VSAM files.||Relative called as VSAM files (RRDS).|
|Records are written in entry sequential order.||Records are written in key sequential order.||Records are written in Record Relative Number order.|
|Duplicate records are allowed to write into the file.||Duplicate records are not allowed to write into the file.||Duplicate records are not allowed to write into the file.|
|Records are not in sorted order.||Records are in sorted order based on key.||Records are in sorted order based on RRN.|
|Record deletion is not possible.||Record can be deleted.||Record can be deleted but the memory not reused.|
|Records accessing is slow because the records only read in sequential order.||Records accessing is faster because the records can read dynamically or randomly.||Records accessing is faster than indexed files as the records can read using RRN.|
|Record key is not available.||Record key is available. Key is user defined and is part of the record.||Record key is available. Key is system generated and is outside of a record.|
|Data can store on tape/disk.||Data can store on disk only.||Data can store on disk only.|
|File opening modes are – INPUT, OUTPUT, I-O, EXTEND.||File opening modes are – INPUT, OUTPUT, I-O.||File opening modes are – INPUT, OUTPUT, I-O.|
|Sequential files are used frequently.||Indexed files are used rarely.||Relative files are used very rarely.|