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For example, in the screenshot below. The "Expenses Claim" app is making use of "j_expense" as the prefix in its forms' table naming.
Figure 1: Form tables
Migrating app form data out would be quite straightforward since it resides in its own set of tables. Depending on the database systems that you are using, you can make use the appropriate tools/clients to export the data out. 
Figure 2: Export App
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- Based on the list compiled in step 1, start new process instance in the new server using the same user with reference to the form record ID. Here's a sample of a process instance that is still running.
Figure 4: Process Instance View
In Figure 4 above, there are 3 vital information we need, and use them to call JSON API in the target server by using JSON API#web/json/workflow/process/start/(*:processDefId). We will also need to copy any workflow variable data over to the new instance too. We can pass on var_* parameters to set the workflow variables' values accordingly.
At this point of time, the new process instance would be waiting at its very first activity.
IMPORTANT NOTE: If you have tools that run right at the start of the process flow, this may cause manipulation of form data state. Take note of potential changes that may occur and devise a way to preserve original data/state. - Once a new process instance is started, note down the process instance ID generated, and we will then need to make use of JSON API#web/json/monitoring/activity/start/(*:processId)/(*:activityDefId) to resume the activity where it supposed to be, in the original server.
Figure 5: Process Instance View Highligting Open Activity Instances
NOTE: Depending on how many pending activities that we may have in the specific process instance, we may need to make multiple calls to this JSON API. Take note that in the first of such call, we will need to set the "abortCurrent" parameter value to "true" so that it aborts the first default pending activity instance. Subsequently, set "abortCurrent" parameter to "false".
IMPORTANT NOTE: The assignee of the resumed activity instance may not be correct if its participant mapping relies on performer of past activities. This is because past activities' data is NOT available in the target server. - In the target server, attempt to continue with the process assignment, as usual, through List Inbox Menu or Inbox Menu in your app, ideally, to the very end, to validate that it is working as expected.
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