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Updating a Sequential File
Posted: Tue Mar 19, 2013 4:02 am
by chandra.shekhar@tcs.com
Hi,
Is there any way/logic to update records in a Sequential File ?
Posted: Tue Mar 19, 2013 7:12 am
by chulett
The short answer is no. You read in the file, update whatever needs updating and then write the result out to a new file. Of course, you could rename the new back to the old when you are done.
Posted: Tue Mar 19, 2013 7:27 am
by chandra.shekhar@tcs.com
I am too doing the same, but I thought better to ask than regret later.
![Wink :wink:](./images/smilies/icon_wink.gif)
Posted: Tue Mar 19, 2013 7:36 am
by chulett
That's the nature of sequential media.
You may be able to do something magical under the covers with C or something similar but for a "pure" DataStage solution there's no magic that I've ever seen. Of course, our resident Magician may say otherwise.
![Wink :wink:](./images/smilies/icon_wink.gif)
Posted: Tue Mar 19, 2013 1:13 pm
by ray.wurlod
I do this a lot when updating values files of Parameter Sets.
One approach is to overwrite the file entirely, using a Sequential File stage. That's the way I normally do it, particularly when the number of parameters in the Parameter Set is small.
The other is to use a Hashed File stage in a server job, opening the file's parent directory as if it were a table, and treating the file name as a record key. This having been done, the individual "fields" (lines) can be updated.
Posted: Tue Mar 19, 2013 1:15 pm
by chulett
Ah... the second part is where the magic happens.
![Wink :wink:](./images/smilies/icon_wink.gif)