What is the life span of data?

Question

Recently I’ve found myself in a database tangle where management wants the ability to remove data from the database, but still wants that data to appear in other places. Example: They want to remove all instances of the product whizbang, but they still want whizbang to appear in sales reports. (if they ran one for a previous date).

Now I can add a field, say is_deleted, that will track whether that product has been deleted and thus still keep all my references, but over a period of time, I have the potential of housing a lot of dead data. (data that is never accessed again). How to handle this is not my question.

I’m curious to find out, in your experience what is the average life span of data? That is, on average how long is data alive or good for before it gets either replaced or deleted? I understand that this is relative to the type of data you are housing, but certainly all data has some sort of life span?

Answer 1

Data lives forever...or often it should. One common practice is to have end and/or start dates for a record. So for your whizbang, you have a start date (so that it won't appear on sales reports before it's official launch), and an end date (so that it drops off of reports after it's been end-of-lifed). Using the proper dates as criteria for your reporting as well as your applications, you won't see the whizbang except for when you should, and the data still exists (which it should, theoretically infinitely).

As Koistya Navin mentions, moving data to a data warehouse at a certain point is also an option, but this depends in large part on how large your 'old' data is, and how long you need to keep it readily available for access.

Answer 2

Many of our customers keep data online for 2 years. After that it's moved to backup disks, but it can be put online if needed.

Consider adding a column "expiration" or "effective date". This will allow you mark a product as obsolete, but reports will return that product if the time range is satisfied.