Question
Cognizant Worldwide
IN
Last activity: 4 Aug 2025 11:05 EDT
Pega Upgrade - Reason for NonClustered Indexes as default
As part of Pega Upgrade we have noticed that the default approach for Pega is to create NCIs for any new or existing tables. We have faced issues with NCIs in the past for some of the existing tables like the work history tables due to the sheer number of records we have. We had to revert these indexes back to Clustered indexes instead to address performance issues.
As part of the current upgrade that we plan to do, we are still keeping any NCIs Pega has created on new tables introduced. We would like to know however why Pega's default approach is to create NCIs rather than Clustered Indexes?
HCA Healthcare
US
Pega creates non-clustered indexes (NCIs) by default during upgrades because it’s the safer and more flexible option. Clustered indexes physically sort the data in the table, and if Pega sets them blindly, it could impact performance or cause issues especially with large tables like work or history tables. NCIs don’t change the way data is stored; they just help speed up specific queries without reorganizing the whole table. Since every client’s data size and usage patterns are different, Pega sticks with NCIs so that performance isn’t accidentally degraded. You’re still free to convert any of those to clustered indexes later if your system benefits from it, just like you did before