Snapshot and process instance migration overview

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This topic only applies to BAW, and is located in the BAW repository. Last updated on 2025-03-13 12:15

To help better understand the snapshot and process instance migration, this overview shows the involved actions and behaviors.

Migration tasks are performed in the following order during snapshot and instance migration.

Snapshot data is migrated from the source to the target snapshot:

Exposed process variable (EPV) changes are migrated.
Environment variable changes are migrated.
Team users and groups are merged from the source to the target.
The source snapshot is deactivated.
The target snapshot is activated.
The target is set as the default snapshot if the source snapshot was the default.
Undercover agents (UCAs) are activated.

Running process instances are migrated from the source to the target:

Each process instance is locked while it is migrated.
Tasks associated with the instances are migrated.
The process execution context and variables are migrated.
Case folders and ad hoc tasks are migrated.
The token migration policy file is applied.
The task search index is updated.
Monitored events are triggered.

Note: In releases earlier than 2022.0.2, you cannot migrate case solution snapshots and their active process instances. For more information, see Case solution snapshots and their active process instances can't be migrated External link opens a new window or tab

Snapshot data migration: While snapshot data is migrated, various settings are migrated from the source snapshot to the destination. These actions are all performed as one transaction. The data for EPV, environment variables (ENVs), and teams is migrated depending on the following behaviors. After migration, the source snapshot is deactivated and the target snapshot is activated. If the source snapshot was the default, that property is also transferred to the target.

EPV data migration: Runtime EPV changes are migrated from the source snapshot to the target snapshot. An entry is added for each effective date and value pair. Default values set at design time are not migrated. For more information about EPV management, see Managing exposed process values (EPVs).
Note: If the <epv-deploy-default> property is set to true, a runtime EPV change is applied to each EPV during deployment with an effective date of the deployment time and a value equal to the EPV's default value.

Environment variable migration: Runtime environment variable and server configuration settings are migrated from the source to the target snapshot. Default values set at design time are not migrated. The changes to the environment variable or server configuration that occur during run time are migrated from the source if they have a modified date that is more recent than any change that occurred at run time in the target snapshot. A change at run time always overrides the snapshot default settings.

Team migration: The contents of teams from the source are merged with the teams in the target. Any users or groups listed for a team from the source snapshot are added to the team in the target. Dynamic teams cannot be migrated.
Note: If the <disable-team-sync> property is set to true, teams are not migrated.

Process instance migration: Process instances with a status of active, failed, or suspended are migrated from the source to the target snapshot. Each process instance is migrated in its own transaction. Multiple threads process the instance migration work based on the value of the <thread-pool-size> setting.
Tip: Do not use the source and target snapshot processes during migration because doing so could lead to lock contention and failures.; Tasks are migrated depending on the <migrate-tasks> and <defer-ec> settings. Depending on the <migrate-tasks> setting, all task, all tasks except closed ones, or no tasks are migrated. By default, all tasks except closed ones are migrated. When the task is migrated, references to source snapshot objects are updated to target snapshot objects. If <defer-ec> is false, the task execution context is loaded and migrated to the target environment. If objects are missing from the source snapshot, migration failures might occur when the execution context is loaded. If task or execution context migration is skipped, migration occurs the next time the task runs. Business object definition version references are not updated in the task execution context.
Note: If tasks are not migrated, deleting snapshots those tasks refer to is prevented. Certain deprecated task assignment methods lead to dynamic teams which cannot be migrated from the source snapshot. These tasks will block the original snapshot's deletion until they are deleted.
If a token policy file is used, you can move or delete tokens associated with an orphaned activity during the instance migration. Some token migration failures will not prevent instance migration. If this occurs, you can perform the token commands after the instance migration is completed. If all tokens for a process are deleted, the process moves to the completed state. The Process Inspector in the Process Admin Console shows orphaned tokens if any were created from instance migration.

Note: Only running instances that are instantiated from a named snapshot are migrated. Other process instances that are associated with the unnamed snapshots are not considered in process centers. This is because only named snapshots exist in process servers; unnamed snapshots exist only in process centers.