Data Management

Get IT Done: Create stand-alone data marts to get end users off your live production data

Use data marts to isolate and protect production data

IT business applications need data. They create data and they use data. Most organizations have more data than they can effectively manage, and, when users need something, it never seems to be together or in the right format.

Over the past decade, the IT development organization has tried to bring this application data closer to business users. This trend has allowed users to have access to more timely information, and, in many cases, has removed the need to go through the IT organization for queries and reports. However, there are some fundamental architecture decisions that need to be made regarding these data stores and how they can be optimized for different purposes.

Transactional data must still be protected
Transactional data is the live data that the applications need to operate. For instance, the accounts receivable system is being updated all day by Accounts Receivable users. Inventory is being updated as orders are received and shipped. The sales system is updated as orders are received during the day. All of the data that these production applications need to run is referred to as transactional data.

In the push to bring data closer to the users, the IT organization must still be protective of this data. Allowing business users broader access to the data cannot compromise the integrity of the information or negatively impact the production applications. The following case study shows a way to bring this live production date closer to your business clients. This solution allows most users "near-time" access to the data while still allowing direct "real-time" access to the small group that needs it.

A case study
In a previous company where I worked, we had a desire to make all of our business application data available to the business users. This included financial data, customer data, license revenue, education offerings, etc. We had reporting tools available for the end users so that they could write their own queries and reports. All of the data was currently available and used in the transactional systems, some of which ran online during the day and some of which ran only at night. The question was how best to provide access to this data to users.

One alternative was to allow the users to access the data directly from the production applications. This was rejected for two reasons. First, the transactional data was stored in a manner that was optimized for the computer application. This was not the most intuitive way for business users to access the information. One of our applications, for instance, seemed, from the outside, to store data in two or three database tables. However, on closer inspection, the data was actually broken down into dozens and dozens of tables, all connected by a set of primary keys and foreign keys. This database structure probably made perfect sense for the application. However, if we would have turned the users loose on these tables, there's no way they could have understood the data and the relationships in the tables. If they could have written reports that accessed the data, there's no telling whether they would have received the reporting results they expected.

The second reason that the transactional data was not used was because of contention issues. The business users were located all over the United States. We didn't want these users trying to access the transactional data while the production systems were running live. Reporting can be very resource intensive, especially when accessing multiple databases. We felt that we were at risk of having the production processes slow down noticeably if users were cranking out reports from the same databases. This would not have been acceptable when people were utilizing the applications to get their jobs done.

Use a reporting data mart when instant access is not required
We quickly realized that we would not be able to make all of this data available to the business users directly from the transactional systems. Instead, we looked at an approach using data marts. Since most of the relevant data that the business people wanted was customer-related, we proposed the creation of a Customer Data mart. We called this a data mart, instead of a data warehouse, since our data did not take up a lot of space, and we didn't utilize formal data warehouse techniques or tools. A data mart is a smaller entity, usually created from a data warehouse and used for reporting and query purposes. We did not start off with a formal warehouse, but the end result was still to allow end user reporting and queries.

Every night, we dumped the relevant transactional database tables into our Customer Data mart. The Customer Data mart was structured and optimized for reporting ease, and it was disengaged from the production systems. This allowed us to provide access to all of the data that our business people would be interested in reporting on, in a format that was much easier to understand from a human perspective.

There are trade-offs to building a redundant data store
There are two trade-offs to this approach. The first is that you must create redundant data stores. In other words, the same data that was in the production transactional tables was also in the Customer Data mart. Why is redundancy a concern? With the size of the tables we were working with, it really has nothing to do with the extra disk space, since the cost of storage is so cheap. The concern comes in having to keep multiple data stores in sync.

For instance, if our transactional system said that we had revenue of twenty million dollars last month, we needed the Customer Data mart to reflect that same amount. If you have duplicate data stores that produce different results for whatever reason, the support staff will spend a lot of time tracking down the discrepancies. The other concern is that if the structure of the transactional data changes, you have to change the data mart structure as well. This could end up causing twice the effort whenever a data structure changes.

We were able to overcome the first redundancy problem of keeping the data in synch by reloading a fresh copy of the transactional tables every night. In other words, we would load the current year's sales data today and then load a completely new copy of the current year's sales data tomorrow and a completely new copy the following night. This is a much cleaner approach than having to worry about processing adds/changes/deletes. However, our database tables were small enough that this was a practical solution. If your data stores are too large, this is not always an effective option.

The second trade-off of building a separate Customer Data mart was one of timeliness. Obviously, if you update your reporting data store on a nightly basis, the data can be as much as one day old. This is a small trade-off, and actually was more than acceptable in our organization. However, if you need the reporting data available in real time (or very close to real time), you may be required to perform multiple updates to your data mart during the day.

Some business users still need real time access
The last part of the solution involved allowing some users to actually access the live production data. For instance, our financial analysts needed real-time access during the monthly closeout process. They needed to create financial reports for management and make sure everything was properly closed out and balanced. Sometimes, this required multiple system updates during the day, as well as manual entries. They needed to be able to run a system update and then query the data immediately. If the data was not correct, they might make additional updates, and come right back in and validate that everything worked. These people were given real-time access to the production data. Having access to last night's data was not good enough for them. However, this level of access was kept to a minimum and did not seem to have a negative performance impact on the production application.

Users are demanding real-time or near-time access to your production data. They also want to get their hands on the data themselves, without having to go to the IT department each time for custom reports. However, your IT staff has a legitimate concern with how these real-time queries will impact the smooth running of your production business applications.

The purpose of this column is to show how both of these legitimate business needs can be accomplished using a two-pronged approach:
  1. Establish a separate data store for reporting purposes and end user queries. Depending on the diversity of the reporting needs and the number of users, you may need multiples of these data marts that are optimized for certain types of reports and queries. These data marts can be created rather quickly without the pain, costs, and complexities of a full-blown data warehouse. This data is "near-time," which means it is close to real time and close enough for the information needs of these end users.
  2. Allow a very small number of end users to have controlled access directly against the production data. This provides the smaller group with actual real-time access, while minimizing (but not eliminating) the potential contention problems.

This approach requires you to duplicate date, which is much less of a problem today than it was twenty years ago. Today, however, it makes great sense to isolate data in a separate data store for reporting and analytical purposes—trading the cost of redundancy against the higher benefits associated with having the data directly accessible to the business users.

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