append, new, or overwrite
append, the default setting, instructs Setup to append to an existing uninstall log when possible.
new, which corresponds to the behavior in pre-1.3 versions of Inno Setup, instructs Setup to always create a new uninstall log.
overwrite instructs Setup to overwrite any existing uninstall logs from the same application instead of appending to them (this is not recommended). The same rules for appending to existing logs apply to overwriting existing logs.