| Sequential files are QSAM files. |
Indexed files are VSAM files. |
Relative files are 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 be written into the file. |
Duplicate records are not allowed to be written into the file. |
Duplicate records are not allowed to be written into the file. |
| Records need not be in sorted order. |
Records are in sorted order based on key. |
Records are in sorted order based on RRN. |
| Record deletion is not possible. |
Records deletion is possible. |
Records deletion is not possible, but the memory will not reused. |
| Accessing records is slow because the records can only be read in sequential order. |
Accessing records is faster because the records can be read dynamically or randomly. |
Accessing records is faster than indexed files as the records can be read using RRN. |
| The key concept is not available. |
The key is available. The key is user-defined and is part of the record. |
The key is available. The key is system-generated and is outside of a record. |
| Data can be stored on tape/disk. |
Data can be stored on disk only. |
Data can be stored on disk only. |
| File opening modes are – INPUT, OUTPUT, I-O, and EXTEND. |
File opening modes are – INPUT, OUTPUT, and I-O. |
File opening modes are – INPUT, OUTPUT, and I-O. |
| Sequential files are used frequently. |
Indexed files are frequently used. |
Relative files are used very rarely. |
