Since JIRA 7.1.4, the default dbconfig.xml settings include:

<pool-test-on-borrow>false</pool-test-on-borrow>

(described more in Health Check: Database Connection Settings)

However, in our documentation, examples for dbconfig.xml do not appear to have been updated to include this.

For example:

• Connecting JIRA applications to MySQL (7.3)
• Connecting JIRA applications to MySQL (7.2)
• Connecting JIRA applications to MySQL (7.1)
• Surviving connection closures (7.3)
• Connecting JIRA applications to SQL Server 2014 (7.3)

The above is not an exhaustive list, just the ones I have checked so far. This does appear to have been updated in our PostgreSQL examples.