Hi,
You will need to categorize the tickets. some issues will be generated as a result of user error and some due to program bugs. In any case there should be a resolution within a stipulated period. For example one of my clients have defined a period of 3 working days, maximum by which a resolution should be provided against a ticket. If the ticket requires some bug fixing or abap development then the same needs to be converted into a change request and monitored separately.
Regards,