Re: Cobol's File System Vs. RDBMs...

On Jul 25, 7:37 am, softWare design <sabra...@xxxxxxxxxxxxx> wrote:
On Jul 24, 11:17 am, Howard Brazee <how...@xxxxxxxxxx> wrote:



This leads me to ask:
1.   What do you man by columns in an index file?
2.   What is the relationship between being open or closed and being
able to add columns?

Suppose I want to change my data model by adding a column
to a table (field to a file record). With a relational database
I add the column and the job is done.  Any program that needs
to work with that new column can on-the-fly, and any existing
programs that do not care about the change stays untouched.

The Cobol index file system is considered to be Closed simply
because it requires a knowledge of the file definition/structure,
in order to access the stored data.  An open file system should
allow privileged users to access the data and generate queries
on-the-fly in the desired format they need, and facilitates any
column insertions without the need to write special programs.

You seem to be confused between what you call 'my data model' and the
business's data model. If you have specific needs then you can extract
data from the business system and add your own data.

If you want these 'extra columns' to contain _meaningful_ data then
you would need to change the business system (input screens, update
processes) to maintain these items correctly, and not just slap on a
couple of extras and hope.

Whether the system is 'open' or 'closed' certainly does depend on
whether the system provides descriptions of the data and means to
access it. This is _NOT_ a function of the file system, but of the
application and the administration.

My COBOL systems that are still based on indexed files provide a
'report writer' interface that allows for printed reports, CSV files
and even HTML to be created by the user and has an interface that
gives the user the ability to create such reports using a GUI.

Fujitsu COBOL indexed files can also be read by Crystal Reports. All
that is required is that the developers provide the schemas.

RDBMS generally do provide the column names but this is only part of
the issue, it is also necessary to understand what the data is.

.

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