Reading C-ISAM without data dictionary
Posted 23 February 2004 - 03:06 AM
My customer has an application using C-ISAM as its data file but no source code and the owner of the application has already gone out from business .
Is it possible to get data from C-ISAM file on AIX without its file's definition ? I have searched from old topics and found that the .dat file is just flat file. If I read the .dat file like sequencial file then can I using substring to extract data from it ?
Posted 23 February 2004 - 07:48 AM
You will need to guess the lengths of the variables and map the file first to get it to work correctly, but that shouldn't be too much of a problem.
Check out their website for more info. It's under Products - Intelligent Adapters.
Posted 23 February 2004 - 11:52 AM
Is this a ProIV application?
In C-ISAM files, numeric fields are generally stored in some kind of BCD (binary coded decimal). One numeric type that ProIV uses with C-ISAM is "COMP3".
There are previous posts on this forum on how to decode a COMP3 field, such as:
If the application is not ProIV, the numeric fields may be stored in another format. C-ISAM has a decimal type built in. The C-ISAM manual is available from IBM at:
Or the Version 5 one:
Posted 23 February 2004 - 05:15 PM
If you're just migrating data rather than trying to interoperate with the old application you might consider writing a "one off" C program - if there's a C programmer handy.
If you know actual values for a subset of records, you can usually use the od (dump) command to look at raw C-ISAM .dat files and have a pretty good guess as to what's going on.
Note that in the (fairly rare) case variable-length C-ISAM is in use, not all the data is in the .dat files - some of it is floating around in the .idx files.
Posted 24 February 2004 - 07:54 AM
Hope this helps
Posted 25 February 2004 - 02:06 AM
There is an U/SQL adapter to extract data to windows' application but it doesn't have data dictionary for all files and also may be it contains the different version of data dictionary. So I try to find out what I can get the most from .ufd file.
Thank you very much for all of your suggestions.
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