Generally speaking, a service level agreement is a contract between an application service provider and a customer that certifies in measurable terms exactly what services will be furnished and at what cost. Reliability is key for any business operation and ASPs are no different in attempting to provide the best possible service. A company usually tries to spell out its performance and reliability in its product literature or on its Web site through customer testimonials and user experiences. But you could do your own fact checking by actually talking to a few of the company's customers yourself. You should also check the SLA to ensure that there are penalty provisions in there in case of non-performance.
Security is perhaps one of the most critical areas to both ASPs and their customers.
A company needs to ensure that their data is stored properly and that provisions are in place to prevent loss or unauthorized access to that data. If a customer lacks specific hardware or software, the ASP will usually provide it. A company should also ask about backups and data storage in the event that a disaster occurs that deletes or destroys data or there is an unexpected loss of service. Provisions should be in place to regularly back up the data that is stored on the ASP servers. Minimal downtime is a critical factor to be considered.