When upgrading JIRA, one points the new JIRA installation at the old JIRA database. JIRA will automatically make any structural database modifications required to support new JIRA features.
To be safe, JIRA first tries to create an XML backup of your data at the point just before the upgrade. This would allow you to 'roll back' to the old JIRA version, should anything go wrong.
Sometimes the automatic XML backup procedure fails, often resulting from characters in the database which cannot be represented in XML — such as non-displayable control characters that have been 'cut-and-pasted' into a JIRA field.
In these circumstances, you can force the upgrade to proceed by editing your
jira-config.properties file (in the JIRA Home Directory) and setting the property
See Making changes to the
jira-config.properties file for more information.
After having successfully upgraded JIRA, it is best to remove this property (or disable it with a '#') as it should no longer be required.