Updating plugins without data loss

[psde]

plugin should consist of deactivation function which should not delete the stored data.
uninstall function should remove stored data.  [see this thread - it can be of some help]

see also MyBB Plugins Explained & advanced plugin development

Thanks for your answer. My plugin already uses the _activate() and _deactivate() functions, but (as the documentation recommends) I do not alter any tables when (de)activating.

My question was how I should design the update process, when the admin is installing a new version of my plugin. As there is no _update() function, in which I could modify the plugins settings rows in the database, I am not sure how to do this.