Joined: 26 May 2005 Posts: 28 Location: Northern VA, USA
Sararaju, it's all about the data. RRDS requires fixed-length records with either a key that increments nicely in one direction only or some form of metadata that "remembers" which relative record is where.
RRDS works nicely for a tape management system, but would be a tough fit for a payroll system.
Why? Because each tape volume can be adequately described with a fixed number of fields of a fixed length.
A payroll system deals with people, and it's hard to fit people into nice, even slots. Here in the US, tax requirements change with locality, marital status, number of dependents, and other things. People's names are varying lengths (unlike tape VOLSERs), their street addresses are varying length (unlike tape library slot numbers), their number of dependents may vary (a tape may have one and only one volume each chained before it and after it).
A small example, to be sure. Real world examples abound.