Upgrade Cognos without upgrading Reports

[cognostechie]

There is a company where the BI manager always installs the latest version of Cognos as soon as it is released but never upgrades the reports. He didn't even know that reports should be upgraded until I told him. Most of the reports are written in version 8x and 10x. While IBM says that they would run in newer versions even if not upgraded but this time I saw some reports stopped running showing syntax errors in the latest version while the same reports are running in the prior version.

Any thoughts? It maybe that the SQL generated in the latest version is slightly different than the earlier one.

[dougp]

My experience has been that report upgrades are typically not needed.  But I like to get new features -- like moving from 10 to 11 and enabling interactivity -- so that my users can have more streamlined workflows.  I also converted as much as I reasonably could from CQM to DQM to prepare for a possible move to the IBM Cloud.  One thing I have found is that any of these upgrades can cause problems.  Reports must be reviewed.  In my environment, with 12,000 reports, 3000 distinct users total, 250 distinct users per day, and hundreds or thousands of report runs per day, I let users do the "testing" in the normal course of their duties.  This works for me because I find that most report problems can be corrected quickly.  (Keep in mind that this is in the context of system upgrades.  Naturally, if we're making database changes, reports get tested before inflicting them on users.)

One thing I have seen -- and I think this relates to DQM -- is that performing multiple layers of calculations in a query can get a little sketchy.  An example is if you create a data item that summarizes another data item that is calculated from a third one that is sourced from an upstream query and use it as a filter.  While this type of thing worked flawlessly for years, I have found that some are failing in recent Cognos versions.  The solution is to break the steps into separate queries (Query1 -> Query2 -> Query3) to get the aggregation correct at each stage.

[cognostechie]

Thanks for sharing your knowledge. That makes sense because Cognos would generate the SQL based on the recent version and every version of every programming language has some changes in the way it gets compiled by the compiler and subsequently executed by the database. I have spent quite a bit of time comparing the SQLs generated for the same report in different versions and found some changes.

I think the reports should be upgraded as a best practice, to inherit the newer features and to prevent them from stop working.