When doing an upgrade from Cognos 7 to Cognos 8 there are two options, use the Cognos provided migration tools to do a "lift and shift" or rebuild all frameworks and reports from scratch. Clients want to choose the "lift and shift" option and for good reason. It seems like it would go faster, require less work and be more cost effective. Is it really?
The lift and shift method may provide quicker results, but does it really require less work and is it more cost effective? In my experience the answer is almost always no. Quality suffers, best practices are not followed, and perhaps most importantly, any mistakes made in the old version are replicated. When evaluating the approach, the following things should be considered:
- How many catalogs does the legacy environment have? Most of my clients have, over time, accumulated multiple catalogs that are essentially the same but have been tweaked to meet a specific reporting need. In the new framework world, these redundant catalogs should be merged into one version of the truth. If this is not done, maintenance costs skyrocket and administration and code promotion becomes a serious pain point.
- Best practices - The Cognos catalog migration tools do not move data into a framework that follows best practices. Only two layers of abstraction are provided requiring additional development work to get to a 3 layer model. If these changes are made to the framework after migration, all migrated reports will likely need to be modified to support the changes.
- Cardinality between query subjects may not be accurate after a migration.
- Many of the new features of the Studios are not leveraged during the migration leaving reports looking stale.
So if the conclusion is to stay away from a straight migration using the provided migration tools then is there a place or reason to use the migration tools at all? Simple stated - yes. The migration tools can be of tremendous help when doing the upfront planning and analysis for the upgrade. In the case where documentation of the legacy reporting environment is limited or non existent, quickly migrating catalogs gives you an easy way to graphically view relationships between query subjects as well as better understand the data at hand. If there are multiple catalogs to review, having them available in Framework Manager makes comparisons and merge analysis much more straightforward. Without question, using this information as input to the future state framework design jumpstarts the upgrade and adds value immediately.