Converting CPU Seconds, Old Node Type to New Node Type - comment by carrie

If your average CPU time has increased after an upgrade there are several factors that could be responsible for this:
 
- While you may have more CPUs per node after the upgrade, it is possible that each CPU by itself is less powerful.   Under those conditions, more work could be accomplished system-wide with the new config, but each CPU second would do less work than before, so more CPU seconds would be required to complete a query.  You can check with your CS people at your site or talk to your account team to find out if your individual CPUs are less powerful on the new configuration.
 
- It is possible that more data has been added onto the platform since the upgrade so each individual query is accessing more data and doing more work.  To look into that, check the estimated rows processed per query in the explain, before and after, or the IO counts in DBQL.  Also you can cross check table sizes before and after the upgrade.
 
- It's possible that a different mix of queries are running since the upgrade took place, queries that are more complex and do more work.
 
-- It is possible that workload mangement options have changed since the upgrade.  Perhaps queries that were poorly written before the upgrade were being aborted or rejected before they started to run, but that is no longer happening post-upgrade.  Check all workload management settings for changes such as that.
 
- Query plans may be different after the upgrade. It is possible that some queries now have plans that are not optimal and are resulting in more work being done in the database. The optimizer uses the hardware configuration as input into creating the plan.  Changes to the number of AMPs can lead to different join geographics and sequences.  Statistics need to be recollected after the upgrade to ensure you are getting the best possible plans.  If there are gaps in the statistics collection strategy before the upgrade, it is possible that after the upgrade those gaps in statistics collection are causing more problems because of the hardware changes.  You can look for ways to improve statistics collections so they are more aligned with standard recommendations.
 
There may be other causes for what you are seeing.  Open an incident with the support center or bring in professional services expertise if more support is required in identifying the source of the discrepancy.
 
Thanks, -Carrie