For upgrades of Pega Infinity release 8.4.2 or later to release 8.5.1 or later for Pega Cloud Services, and for on-premises upgrades on Tomcat and PostgreSQL, you experience near-zero downtime. The latest upgrade process enhancements include improved monitoring to prevent issues and rolling upgrades and procedures that maintain high availability so that you can continue to work on your applications during the upgrade. It is expected that some application use cases might not be available while the upgrade is in progress.

The list of use cases that are described in this article is not comprehensive. Based on your Pega application, you might encounter similar use cases that have a dependency on data changes that are introduced in the new version. Pega recommends that you consult your developers to identify and plan your approach to address the use cases that apply to your application.

Impact of DDL and DML upgrade changes on application use cases

The following Data Definition Language (DDL) and Data Manipulation Language (DML) upgrade changes might impact use cases until the upgrade is fully complete:

• Auto-complete and drop-down lists that display values from data types do not display the values that were added or modified in the new version.
• Processes such as utility shapes that rely on the latest records that were added to the data types fail. 
  The process cannot find the corresponding data record or the data type itself.
• New work baskets are not imported until the upgrade process modifies the data schema. 

Pega recommends the following general approaches to address DDL and DML upgrade changes: 

• Package the data records that are modified or added, and then import them into the upgraded environment.
  For more information, see Migrating upgrade fixes to production.  
• Avoid running use cases that are impacted by DDL and DML upgrade changes.

Impact of rolling restart on application use cases

During the rolling restart, changes might be introduced by using the new application version. The potential exists for these case changes to be processed by the prior rules which can lead to incompatibility.

Examples include the following:

• When the flow rule introduces a new shape into the case type  
• Processing cases when case type rules introduced new stages (primary or alternative)
• Processing cases after their data model has been auto-updated to the new version
• Processing cases when the cases have been created with the new data model

Discontinue processing any use cases that meet these criteria until the upgrade completes.

Application-specific information

In addition to the use cases listed above, there are application-specific use cases. To find information on your application use cases, click the link below that corresponds to your application.