Summary -
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. |