Issue Summary

JCMA allows you to run a migration to a target site, and immediately after create another migration plan for the same site. Concurrent migrations to the same site often result in issues that must be addressed by database operations.

Steps to Reproduce

1. Create a JCMA migration plan to target Site A.
2. While the first migration to Site A runs, create another migration plan for Site A.
3. There are chances that the migrations would spin indefinitely or take hours to finally stop due to concurrency issues.

Expected Results

You should not be allowed to create inconsistencies due to concurrent migration plans.

Actual Results

The migration assistant allows you to create a second migration for the same site, even if there is one ongoing. This often causes future migrations to be stuck.

Workaround

Manually changing the migration status in the database, which is risky.