It almost sounds contradictory and it’s certainly counter-intuitive. Nevertheless the technology is real enough and it’s getting traction. Clearpace is a company I’ve been tracking for quite a few years now. It was formed to build on and exploit in-memory database technology, but it had difficulty finding a compelling commercial application area. Eventually the company hit on database archiving and it has found a market for its NParchive software among large companies that manage big databases.

So how can in-memory database technology be applied to database archiving?

Let’s begin by explaining in outline how the in-memory database technology works.

This is illustrated in the above diagrams. Instead of storing database tables as tables, NParchive converts the tables into a kind of tree structure. The top diagram shows the first record in a table being stored; First Name – Peter, Last Name – Smith, Company Classification – Pharmaceutical, Salary – $40,000. Not only are the values stored but also the link between these values which preserve the fact that it is a distinct row. The second diagram shows the second record; Paul, Smith, Finance, $35,000, being stored. Because the value Smith already exists it doesn’t need to be stored. The third diagram shows the third record John, Brown, Pharmaceutical, $40,000, being stored.

Using this method of organizing the data you reduce the space it occupies considerably because you only store as many values for any column as the cardinality of the column. This is not the only advantage of storing the data this way. You can also get the results of a query on the data simply by “walking the tree.” In effect, you can compress the data considerably without damaging your ability to query it.

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