When upgrading from the Exalate 3.X version to 4.X the following error is raised
We are using Atlassian Active Objects framework to interact with the MS SQL database. A problem with a unique constraint on one of our database tables during the upgrade causes the error.
U_AO_08F1AF_INSTANCE_NAME is a stale object, which relates to the Exalate but is created by Active Objects framework of JIRA Server instance. It fails to be cleaned up in the course of the upgrade.
Drop the index U_AO_08F1AF_INSTANCE_NAME manually and re-install the Exalate app.