IBM BPM, V8.0.1, All platforms > Installing, deploying, and undeploying applications in the runtime environment > Installing process application snapshots > Migrating instances
Data migration rules
If running instances of the business process definitions that you are installing are discovered on the target process server, the target server migrates data according to the migration option you choose.
See Migrating instances to understand the migration options available when running instances are discovered.
Regardless of the migration option you choose, the process server copies environment variables from the installed snapshot or snapshots.
If environment variable values have been changed from the defaults, the values most recently set are the ones used. In the case where an installation service sets the values, those values are considered the most recent and are the values used.
If you choose to migrate running process instances to a new version (snapshot), the process server performs the following actions:
- Copies exposed process values (EPVs) from all installed snapshots.
If EPVs have been changed from the defaults, the values most recently set are the values used. In the case where an installation service sets the values, those values are considered the most recent and are the values used.
EPVs in referenced toolkits are copied only if the referenced toolkit is not already available on the target server.
- Merges the participant group members (users/groups) from previously installed snapshots into the snapshot that now contains the migrated instances. If the participant group has been updated in a snapshot in the Process Center Console (for example, a user or group was added or deleted), those changes are not applied during the merge process.
Users added by an installation service before the migration are not overwritten. However, if the participant group on the target server is empty or does not exist (meaning that it was added in the new snapshot), it is "seeded" with the users and groups from the Process Center. This is considered a "seed" because the real bindings will likely be updated after the installation.
- Moves the Default designation from the snapshot of the running instances to the newly installed snapshot. This action takes place only if the snapshot of the running instances has previously been designated as the Default snapshot.
Deactivates the snapshot that originally contained the running instances.
Related concepts:
Migrating instances