Thanks Raj, yes although the changeset comment could be used to reflect that information too. When you span multiple JIRA tickets for a change do you have any pattern? How do you coordinate numbers between them?
Given the insignificance of the identifier actually needing to be sequential I'm wondering if a simple GUID auto generated is even better with the changeset comment reflecting other information e.g. the date it was originally created / JIRA entities and so on. You would never have to worry about whether an identifier was really unique too.