Can we connect same JIRA MS SQL database to multiple instances of JIRA? We intend to migrate and upgrade JIRA to new application server

[Nic Brough -Adaptavist- · Accepted solution]

Absolutely not, you'll destroy your data.  I'm assuming that you mean JIRA Server though, and not JIRA Data Centre, which will work, sort of, but then you don't need to be migrating...

You need to work with copies of the data to do this, or do the "complete shut down, move and start new system" process.  See https://confluence.atlassian.com/adminjiraserver071/migrating-jira-applications-to-another-server-802592269.html